Browsing by Author "Sharma, Vishakha"

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Abnormal Leaf morphologies associated with primary and secondary vein patterning defects in Catharanthus roseus: mid-vein defect converts simple leaf into binate compound leaf
(Springer, 2013) Kumar, Sushil; Sharma, Vishakha
Simple petiolated leaves are formed on the wild type plants of apocynaceous medicinal-cum-floricultural species Catharanthus roseus. A C. roseus variant line homozygous for two loss-of-function mutations, an induced leafless inflorescence (lli) mutations and a natural bisected leaf (bil) mutation, was isolated on account of its unique leaf bisection phenotype which was characterized. The lli bil phenotype was highly penetrant but poorly expressed. Only about one-fourth of leaves of lli bil plants were bisected. Leaf bisection was correlated with premature termination of midvein. Degree of bisection varied from a nick at the apex of lamina to formation of two complete leaflets. The notch in 43 % of the bisected leaves bore a pin-like apical adventitious growth. The features of bisected leaves showed that midvein was essential for symmetrical development of smooth lamina spans on its either side; although the development of spans was independent. Several lateral veins emerged from proximal midvein and grew acropetally. Lamina development in the proximal region failed in the absence of local lateral veins. Bisected leaves were also formed as bi-lobed simple leaves, each lobe having its own primary (mid) vein arising from proximally bifurcated midvein. Also formed were completely bisected leaves. In these binately compound leaves, each leaflet had its own petiolule attached to the leaf petiole. The lli bil genotype of C. roseus perhaps provides the only example of a compound leaved variant evolving from a simple leaved species. This phenotype of lli bil leaves supports the suggestion that simple leaf form was ancestral in angiosperms.
Agronomic characteristics of autumn and winter seeded photoperiod insensitive spring wheat in agro-climate of north-west India
(Indian National Science Academy, 2012) Kumar, Sushil; Sharma, Vishakha; Chaudhary, Swati; Kumar, Arvind; Kumari, Renu
An analysis of vascular system in the compound tendrilled afila leaf in Pisum sativum
(National Institute of Science Communication and Information Resources-NISCAIR, 2014) Sharma, Vishakha; Kumar, Arvind; Kumar, Sushil
Recent work on the venation patterning and morphogenesis of leaf/leaflet has posed the question how different are these in tendrils, which are another type of vegetative lateral organ. Here, the venation patterns of leaflets, stipules and tendrils were compared in the model species, P. sativum. Unlike reticulated venation in leaflets and stipules, venation in tendrils comprised of one or more primary veins. A few secondaries were attached to a primary vein, mostly distally. Bilaterally symmetrical secondary veins were rare. The primary veins in tendrils were daughter strands from dichotomously divided mother veins in rachis, connected finally to vascular strands in stem. A tendril received primary vein from one or more mother strands. Some mother strands contributed primary veins to proximal, distal and terminal domain tendrils of af leaf. The tendrils shared the multi-primary vein character with stipules. Vein redundancy provided a mechanism for survival of tendril/leaf against injury to some of the veins/mother veins. The presence of aborted primary veins that did not reach apex, rows of cambium cells attached to primary vein(s) at apex, the pattern of attachment of primary veins to mother veins and cessation of vein growth in apical direction in aborted tendrils of af lld genotype indicated that the growth of primary veins and tendril was acropetal. Loss-of-function of AF extended the repression of TL and MFP genes on leaflet development from distal and apical domains to proximal domain of leaves in af mutants.
Auxin transport inhibitor induced low complexity petiolated leaves and sessile leaf-like stipules and architectures of heritable leaf and stipule mutants in Pisum sativum suggest that its simple lobed stipules and compound leaf represent ancestral forms in angiosperms
(Indian Academy of Sciences, 2013) Kumar, Arvind; Sharma, Vishakha; Khan, Moinuddin; Hindala, Mali Ram; Kumar, Sushil
In angiosperms, leaf and stipule architectures are inherited species-specific traits. Variation in leaf and stipule sizes, and forms result from the interaction between abiotic and biotic stimuli, and gene regulatory network(s) that underlie the leaf and stipule developmental programme(s). Here, correspondence between variation in leaf and stipule architectures described for extant angiosperms and that induced mutationally and by imposition of stress in model angiosperm species, especially in Pisum sativum, was detected. Following inferences were drawn from the observations. (i) Several leaf forms in P. sativum have origin in fusion of stipule and leaf primordia. Perfoliate (and amplexicaul and connate) simple sessile leaves and sessile adnate leaves are the result of such primordial fusions. Reversal of changes in the gene regulatory network responsible for fusion products are thought to restore original stipule and leaf conditions. (ii) Compound leaf formation in several different model plants, is a result of promotion of pathways for such condition by gene regulatory networks directed by KNOx1 and LEAFY transcription factors or intercalation of the gene networks directed by them. (iii) Gene regulatory network for compound leaves in P. sativum when mutated generates highly complex compound leaves on one hand and simple leaves on other hand. These altered conditions are mutationally reversible. (vi) Simple leaves in model plants such as Arabidopsis thaliana despite overexpression of KNOx1 orthologues do not become compound. (v) All forms of leaves, including simple leaf, probably have origins in a gene regulatory network of the kind present in P. sativum.
Characterization and genetic linkage mapping of the horticulturally important mutation leafless inflorescence (lli) in periwinkle Catharanthus roseus
(Elsevier, 2011) Chaudhary, Swati; Sharma, Vishakha; Prasad, Manoj; Bhatia, Sabhyata; Tripathi, Bhumi Nath; Yadav, Gitanjali; Kumar, Sushil
Catharanthus roseus is a seasonal to perennial garden plant and the exclusive source of the anticancer drugs vincristine and vinblastine. Its horticultural importance is due to the compound racemose inflorescence architecture of branches in which pairs of prominent flowers are subtended by one of the two leaves per node. Here is reported the construction of a molecular framework genetic linkage map and mapping on it of the LEAF-LESS INFLORESCENCE (LLI) locus. It is quantitatively shown that the adult lli mutant plants produce altered inflorescence of improved horticultural value, wherein axes are excessively branched, two flowers are formed per node that are bare of subtending leaves, and several times more open flowers are displayed each day, as compared to LLI plants.
Characterization of variation and quantitative trait loci related to terpenoid indole alkaloid yield in a recombinant inbred line mapping population of Catharanthus roseus
(Indian Academy of Sciences, 2012) Sharma, Vishakha; Chaudhary, Swati; Srivastava, Suchi; Pandey, Richa; Kumar, Sushil
Improved Catharanthus roseus cultivars are required for high yields of vinblastine, vindoline and catharanthine and/or serpen- tine and ajmalicine, the pharmaceutical terpenoid indole alkaloids. An approach to derive them is to map QTL for terpenoid indole alkaloids yields, identify DNA markers tightly linked to the QTL and apply marker assisted selection. Towards the end, 197 recombinant inbred lines from a cross were grown over two seasons to characterize variability for seven biomass and 23 terpenoid indole alkaloids content-traits and yield-traits. The recombinant inbred lines were genotyped for 178 DNA markers which formed a framework genetic map of eight linkage groups (LG), spanning 1786.5 cM, with 10.0 cM average intermarker distance. Estimates of correlations between traits allowed selection of seven relatively more important traits for terpenoid indole alkaloids yields. QTL analysis was performed on them using single marker (regression) analysis, simple interval mapping and composite interval mapping procedures. A total of 20 QTL were detected on five of eight LG, 10 for five traits on LG1, five for four traits on LG2, three for one trait on LG3 and one each for different traits on LG three and four. QTL for the same or different traits were found clustered on three LG. Co-location of two QTL for biomass traits was in accord of correlation between them. The QTL were validated for use in marker assisted selection by the recombinant inbred line which transgressively expressed 16 traits contributory to the yield vinblastine, vindoline and catharanthine from leaves and roots that possessed favourable alleles of 13 relevant QTL.
COCHLEATA controls leaf size and secondary inflorescence architecture via negative regulation of UNIFOLIATA (LEAFY ortholog) gene in garden pea Pisum sativum
(Indian Academy of Sciences, 2012) Sharma, Vishakha; Chaudhary, Swati; Kumar, Arvind; Kumar, Sushil
UNIFOLIATA [(UNI) or UNIFOLIATA-TENDRILLED ACACIA (UNI-TAC)] expression is known to be negatively regulated by COCHLEATA (COCH) in the differentiating stipules and flowers of Pisum sativum. In this study, additional roles of UNI and COCH in P. sativum were investigated. Comparative phenotyping revealed pleiotropic differences between COCH (UNI-TAC and uni-tac) and coch (UNI-TAC and uni-tac) genotypes of common genetic background. Secondary inflorescences were bracteole-less and bracteolated in COCH and coch genotypes, respectively. In comparison to the leaves and corresponding sub-organs and tissues produced on COCH plants, coch plants produced leaves of 1.5-fold higher biomass, 1.5-fold broader petioles and leaflets that were 1.8-fold larger in span and 1.2-fold dorso-ventrally thicker. coch leaflets possessed epidermal cells 1.3-fold larger in number and size, 1.4-fold larger spongy parenchyma cells and primary vascular bundles with 1.2-fold larger diameter. The transcript levels of UNI were at least 2-fold higher in coch leaves and secondary inflorescences than the corresponding COCH organs. It was concluded that COCH negatively regulated UNI in the differentiating leaves and secondary inflorescences and thereby controlled their sizes and/or structures. It was also surmised that COCH and UNI (LFY homolog) occur together widely in stipulate flowering plants.
Coevolution mechanisms that adapt viruses to genetic code variations implemented in their hosts
(Indian Academy of Sciences, 2016) Kumar, Sushil; Kumari, Renu; Sharma, Vishakha
Viruses, the preponderant species, are the agents of horizontal gene transfer between cellular organisms, a major means for generation of genetic variability that drives evolution in varying environments. Recent work on virus × host interaction has led to revision of the conventional idea that the genetic code of the virus and host must be same so that the host translational system facilitates efficient, accurate and complete expression of the infecting viral genome. There is evidence now that differences between the genetic codes of viruses and their hosts are not an absolute barrier to virus multiplication. The recent work on mechanisms by which viruses overcome the mismatch in codon usage of host versus theirs is discussed here contextually. Examples of coevolution of viruses and their hosts, in terms of genetic code usage, discussed here agree with the concept that their evolution is reciprocally driven and therefore suggestive of a kind of long-term interdependent symbiotic relationship between them.
Common and distinguishing characteristics of genes and genomes and their evolution in the genome sequenced legumes
(Indian National Science Academy, 2013) Kumar, Sushil; Kumari, Renu; Sharma, Vishakha; Yadav, Gitanjali
By March 2013, genome sequences have been published for five legume species- Cicer arietinum (pulse crop chickpea), Cajanus cajan (pulse crop pigeonpea), Glycine max (pulse-cum-oil seed crop soybean), Lotus japonicus and Medicago truncatula (both model plants). The genome sequenced legumes belong to the subfamily papilionoideae of the angiosperm family leguminoseae, C. arietinum, L. japonicus and M. truncatula to the galegoid clade and C. cajan and G. max to millettioid clade. These diploid species have 2n number varying from 12 in L. japonicus, 16 in M. truncatula and C. arietinum, 22 in C. cajan and 40 in G. max. Comparisons among their genome sequences have revealed several important properties about structure and evolution of their genomes. Thirty five to 60% of genome is in the form of repititive elements, mainly transposons. Genome carries less than 50,000 protein-coding genes, 56 to 87% in two or more copies. All the five species arose from a common pre-papilionoid parent produced by inter-species hybridization accompanied by whole genome duplication (WGD or allotetraploidy) about 58 million years ago (Mya). Separation of clades and speciation occurred via sequence changes, over a period of > 40 million years. Individual genes underwent substitution and frameshift mutations. Chromosomal level rearrangements involved deletions, inversions, translocations, fission and fusions. There was spread of individual genes or blocks of genes followed by their tandem duplication. Deletion of orthologues was also involved in lineage specific changes. Ancestors of Glycine underwent an allotetraploid event after separation of C. cajan in the millettioid clade about 13 Mya. Developments relating to the applications of legume genome sequence knowledge are also discussed.
Cropping of the artemisinin (antimalarial drug) yielding Artemisia annua cultivars, over a ten year period in the agroclimate of north-west India, has not led to the species becoming a weed
(The National Academy of Sciences, India, 2011) Goel, Richa; Goel, Divya; Chaudhary, Swati; Sharma, Vishakha; Kumar, Sushil
The antimalarial drug artemisinin is extracted from the leaves and flowers, harvested from the naturally growing and cultivated populations, of the asteraceae plant Artemisia annua. The species is indigenous to Chongqing region of China where it is a weed and is found growing into extensive wild populations. It has become naturalized (weed) in several agroclimates of its introduction in Asia, Australia, Europe and North and South Americas. A. annua is now beginning to be cultivated in several agroclimates of India. Agrotechnologies suitable for cultivating A. annua in the Indo-gangetic and North- West Indian plains have been developed and introduced with the farmers. Here, the potential of A. annua becoming a weed, in the areas of its cultivation, has been assessed under the New Delhi agroclimatic conditions. Single plants of A. annua were observed to produce about 0.14×106 viable seeds. Cultivation of A. annua in field plots at two locations and enumeration of plants outside the plots of cultivation over a 10 year period was observed not to lead to escape of the plant into areas adjacent to the plots of A. annua cultivation. It is concluded that A. annua, despite being a prolific producer of seeds, is unlikely to become a weed in the agroclimate of north-west plains region of India. Therefore, subtropical agroclimates such as that of north-west Indian plains offer comparative advantage for the cultivation of the domesticated A. annua for artemisinin production.
Cytosine hypomethylation at CHG and CHH sites in the pleiotropic mutants of Mendelian inheritance in Catharanthus roseus
(Indian Academy of Sciences, 2013) Kumari, Renu; Yadav, Gitanjali; Sharma, Vishakha; Sharma, Vinay; Kumar, Sushil
The 5S and 18S rDNA sequences of Catharanthus roseus cv 'Nirmal' (wild type) and its leafless inflorescence (lli), evergreen dwarf (egd) and irregular leaf lamina (ill) single mutants and lli egd, lli ill and egd ill double mutants were characterized. The lli, egd and ill mutants of Mendelian inheritance bore the names after their most conspicuous morphological feature(s). They had been chemically induced and isolated for their salt tolerance. The double mutants were isolated as morphological segregants from crosses between single mutants. The morphological features of the two parents accompanied salt tolerance in the double mutants. All the six mutants were hypomethylated at repeat sequences, upregulated and downregulated for many genes and carried pleiotropic alterations for several traits. Here the 5S and 18S rDNAs of C. roseus were found to be relatively low in cytosine content. Cytosines were preponderantly in CG context (53%) and almost all of them were methylated (97%). The cytosines in CHH and CHG (where H = A, T or C) contexts were largely demethylated (92%) in mutants. The demethylation was attributable to reduced expression of RDR2 and DRM2 led RNA dependant DNA methylation and CMT3 led maintenance methylation pathways. Mutants had gained some cytosines by substitution of C at T sites. These perhaps arose on account of errors in DNA replication, mediated by widespread cytosine demethylation at CHG and CHH sites. It was concluded that the regulation of cytosine ethylation mechanisms was disturbed in the mutants. ILL, EGD and LLI genes were identified as the positive regulators of other genes mediating the RdDM and CMT3 pathways, for establishment and maintenance of cytosine methylation in C. roseus.
Development of improved horticultural genotypes characterized by novel over-flowering inflorescence trait in periwinkle Catharanthus roseus
(Springer Science, 2012) Kumar, Sushil; Chaudhary, Swati; Kumari, Renu; Sharma, Vishakha; Kumar, Arvind
Floricultural genotypes with new plant architecture were developed in the seasonal/perennial garden plant Catharanthus roseus. The new genotypes were developed by crossing the double mutant line lli egd of C. roseus with two horticultural lines of C. roseus and a line of Catharanthus trichophyllus. As compared to the normal LLI inflorescence architecture in which racemose inflorescence had pairs of flowers subtended by one of the two leaves per node, the lli inflorescence of the new lines was excessively branched and each branch had two flowers per node which were bereft of subtending leaves. The new lines are novel in displaying several fold increased number of flowers on inflorescence unhindered by leaves. In the new floricultural lines the over-flowering lli trait was combined with variation in plant height, petal and eye colors and tolerance to the common fungal diseases.
Ebola virus disease: Biology, diagnosis, treatment and prevention of epidemics
(Indian National Science Academy, 2017) Kumar, Sushil; Kumari, Renu; Pandey, Richa; Sharma, Vishakha
Ebola virus disease (EVD) is a highly lethal contagious disease caused by the negative RNA strand Ebola virus. Reservoired in wild forest animals of Africa, Ebola virus infects humans that come in direct contact of diseased animals and outbreaks of EVD result from person to person spread of infection. A recent EVD outbreak in West Africa has killed several thousand persons. Since Ebola infection will persist in animals, EVD epidemics are expected to continue to occur in future. Infected travellers from Africa can initiate/import outbreaks in countries of other continents. This review describes the properties of the Ebola virus and EVD, the ongoing attempts to develop diagnostics, vaccines and medicines for prevention and cure of EVD and the supportive care that saves some EVD patients. Also discussed are measures that can stop and prevent EVD outbreaks. Need for inclusion of EVD in the education, research, drug and medical equipment manufacturing programmes, of the densly populated countries such as India, is emphasised.
Genetic analysis of structure and function of stipules in pea (Pisum sativum)
(Indian National Science Academy, 2012) Sharma, Vishakha; Sinha, Alok Krishna; Chaudhary, Swati; Priyadarshini, Anupama; Tripathi, Bhumi Nath; Kumar, Sushil
Genetic control of leaf-blade morphogenesis by the Insecatus gene in Pisum sativum
(Indian Academy of Sciences, 2010) Kumar, Sushil; Chaudhary, Swati; Sharma, Vishakha; Kumari, Renu; Mishra, Raghvendra Kumar; Kumar, Arvind; Choudhury, Debjani Roy; Jha, Ruchi; Priyadarshini, Anupama; Kumar, Arun
To understand the role of INSECATUS (INS) gene in pea, the leaf blades of wild-type, ins mutant and seven other genotypes, constructed by recombining ins with uni-tac, af, tl and mfp gene mutations, were quantitatively compared. The ins was inherited as a recessive mutant allele and expressed its phenotype in proximal leaflets of full size leaf blades. In ins leaflets, the midvein development was arrested in distal domain and a cleft was formed in lamina above this point. There was change in the identity of ins leaflets such that the intercalary interrupted midvein bore a leaf blade. Such adventitious blades in ins, ins tl and ins tl mfp were like the distal segment of respective main leaf blade. The ins phenotype was not seen in ins af and ins af uni-tac genotypes. There was epistasis of uni-tac over ins. The ins, tl and mfp mutations interacted synergistically to produce highly pronounced ins phenotype in the ins tl mfp triple mutant. The role(s) of INS in leaf-blade organogenesis are: positive regulation of vascular patterning in leaflets, repression of UNI activity in leaflet primordia for ectopic growth and in leaf-blade primordium for indeterminate growth of rachis, delimitation of proximal leaflet domain and together with TL and MFP homeostasis for meristematic activity in leaflet primordia. The variant apically bifid shape of the affected ins leaflets demonstrated that the leaflet shape is dependent on the venation pattern.
Genetic interaction and mapping studies on the leaflet development (lld) mutant in Pisum sativum
(Indian Academy of Sciences, 2012) Kumar, Sushil; Mishra, Raghvendra Kumar; Kumar, Arvind; Chaudhary, Swati; Sharma, Vishakha; Kumari, Renu
In Pisum sativum, the completely penetrant leaflet development (lld) mutation is known to sporadically abort pinnae suborgans in the unipinnate compound leaf. Here, the frequency and morphology of abortion was studied in each of the leaf suborgans in 36 genotypes and in presence of auxin and gibberellin, and their antagonists. Various lld genotypes were constructed by multifariously recombining lld with a coch homeotic stipule mutation and with af, ins, mare, mfp, tl and uni-tac leaf morphology mutations. It was observed that the suborgans at all levels of pinna subdivisions underwent lld-led abortion events at different stages of development. As in leafblades, lld aborted the pinnae in leaf-like compound coch stipules. The lld mutation interacted with mfp synergistically and with other leaf mutations additively. The rod-shaped and trumpet-shaped aborted pea leaf suborgans mimicked the phenotype of aborted leaves in HD-ZIP-III-deficient Arabidopsis thaliana mutants. Suborganwise aborted morphologies in lld gnotypes were in agreement with basipetal differentiation of leaflets and acropetal differentiation in tendrils. Altogether, the observations suggested that LLD was the master regulator of pinna development. On the basis of molecular markers found linked to lld, its locus was positioned on the linkage group III of the P. sativum genetic map.
Genetics of dioecy and causal sex chromosomes in plants
(Indian Academy of Sciences, 2014) Kumar, Sushil; Kumari, Renu; Sharma, Vishakha
Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and androecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 and WZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.
Genetics of flowering time in bread wheat Triticum aestivum: complementary interaction between vernalization-insensitive and photoperiod-insensitive mutations imparts very early flowering habit to spring wheat
(Indian Academy of Sciences, 2012) Kumar, Sushil; Sharma, Vishakha; Chaudhary, Swati; Tyagi, Anshika; Mishra, Poonam
Time to flowering in the winter growth habit bread wheat is dependent on vernalization (exposure to cold conditions) and exposure to long days (photoperiod). Dominant Vrn-1 (Vrn-A1, Vrn-B1 and Vrn-D1) alleles are associated with vernalization independent spring growth habit. The semidominant Ppd-D1a mutation confers photoperiod-insensitivity or rapid flowering in wheat under short day and long day conditions. The objective of this study was to reveal the nature of interaction between Vrn-1 and Ppd-D1a mutations (active alleles of the respective genes vrn-1 and Ppd-D1b). Twelve Indian spring wheat cultivars and the spring wheat landrace Chinese Spring were characterized for their flowering times by seeding them every month for five years under natural field conditions in New Delhi. Near isogenic Vrn-1 Ppd-D1 and Vrn-1 Ppd-D1a lines constructed in two genetic backgrounds were also phenotyped for flowering time by seeding in two different seasons. The wheat lines of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1a, Vrn-A1a Vrn-B1 Ppd-D1a and Vrn-A1a Vrn-D1 Ppd-D1a (or Vrn-1 Ppd-D1a) genotypes flowered several weeks earlier than that of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1b, Vrn-A1b Ppd-D1b and Vrn-D1 Ppd-D1b (or Vrn-1 Ppd-D1b) genotypes. The flowering time phenotypes of the isogenic vernalization-insensitive lines confirmed that Ppd-D1a hastened flowering by several weeks. It was concluded that complementary interaction between Vrn-1 and Ppd-D1a active alleles imparted super/very-early flowering habit to spring wheats. The early and late flowering wheat varieties showed differences in flowering time between short day and long day conditions. The flowering time in Vrn-1 Ppd-D1a genotypes was hastened by higher temperatures under long day conditions. The ambient air temperature and photoperiod parameters for flowering in spring wheat were estimated at 25°C and 12 h, respectively.
Interaction between cochleata and stipule-reduced mutations results in exstipulate hypertrophied leaves in Pisum sativum L.
(NISCAIR-CSIR, India, 2013) Kumar, Arvind; Sharma, Vishakha; Kumar, Sushil
In the wild type P. sativum, each of the adult plant stem nodes, bears a pair of sessile foliaceous stipules and a petiolated unipinnately compound leaf of 4 to 6 leaflets and 7-9 tendrils. The stipule-reduced (st) and cochleata (coch) single null mutants and coch st double null mutant differ fom the wild type in respectively having sessile stipules of much reduced size, petiolated simple and/or compound leaf-like stipules and no stipules. It is also known that coch leaves are somewhat bigger than st and wild type leaves. Here, pleiotropic phenotype of coch st double mutant was investigated. The morphologies of stipules and leaf were quantified in the field grown plants and microcultured shoots, latter in the presence and absence of gibberellic acid and N-1-naphthylphthalamic acid. The observations showed that as compared to the corresponding plants or shoots of COCH ST (WT) genotype, (a) coch st plants bore leaves in which all the organs were hypertrophied; (b) full complement of leaflets and 3-5 tendrils were formed on leaf; (c) the microcultured coch st shoots were taller despite lower number of nodes, and (d) they also produced leaves in which all the organs were bigger and the ratio of leaflets/tendrils was higher. It was concluded that in coch st double mutant (a) ST function is essential for stipule primordium differentiation, in the absence of COCH function and (b) absence of negative feedback loops between simple stipules and compound leaf for metabolite utilization allows hypertrophied growth in leaves.
Interaction between COCHLEATA and UNIFOLIATA genes enables normal flower morphogenesis in the garden pea, Pisum sativum
(Indian Academy of Sciences, 2011) Kumar, Sushil; Sharma, Vishakha; Chaudhary, Swati; Kumari, Renu; Kumari, Nisha; Mishra, Poonam
The simple stipules, leaflet and tendril bearing imparipinnately compound leaf blades and zygomorphic flowers, produced on stems of the diploid (2n = 14; ≥ 5000 Mbp nuclear genome) papilionoid Fabaceae plant Pisum sativum, are serving as unique and highly informative models for the dis- section of plant developmental programmes. The growing information has revealed that the processes of stipule, leaf and flower morphogeneses are genetically interconnected in P. sativum (Hofer et al. 1997; Yaxley et al. 2001; Wang et al.2008; Kumar et al. 2009).