Institutional Publications

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Mediator subunit OsMED14_1 plays an important role in rice development
(John Wiley & Sons, 2020) Malik, Naveen; Ranjan, Rajeev; Parida, Swarup K.; Agarwal, Pinky; Tyagi, Akhilesh K.
Mediator, a multi‐subunit coactivator complex, regulates transcription in eukaryotes and is involved in diverse processes in Arabidopsis through its different subunits. Here, we have explored developmental aspects of one of the rice Mediator subunit gene OsMED14_1. We analyzed its expression pattern through RNA in‐situ hybridization and pOsMED14_1:GUS transgenics which showed its expression in roots, leaves, anthers and seeds prominently at younger stages, indicating possible involvement of this subunit in multiple aspects of rice development. To understand developmental roles of OsMED14_1 in rice, we generated and studied RNAi based knockdown rice plants which showed multiple effects including less height, narrower leaves and culms with reduced vasculature, lesser lateral root branching, defective microspore development, reduced panicle branching and seed set, and smaller seeds. Histological analyses showed that slender organs were caused by reduction in both cell number and cell size in OsMED14_1 knockdown plants. Flow cytometric analyses and expression analyses of cell‐cycle related genes revealed that defective cell‐cycle progression led to these defects. Expression analyses of auxin related genes and IAA immuno‐localization study indicated altered auxin level in these knockdown plants. Reduction of lateral root branching in knockdown plants was corrected by exogenous IAA supplement. OsMED14_1 physically interacts with transcription factors YABBY5, TDR and MADS29, possibly regulating auxin homeostasis and ultimately leading to lateral organ/leaf, microspore and seed development.
Genome-wide investigation and expression analysis suggest diverse roles of auxin-responsive GH3 genes during development and response to different stimuli in tomato (Solanum lycopersicum)
(Springer Science, 2012) Kumar, Rahul; Agarwal, Priyanka; Tyagi, Akhilesh K.; Sharma, Arun K.
In plants, auxin-mediated responses are regulated by diverse proteins. One such class of proteins, i.e. GH3, is involved in the conjugation of IAA to amino acids and provides a negative feedback loop to control auxin homoeostasis. In order to have a better understanding of the mechanism of the auxin action, 15 genes encoding GH3 members were identified using existing EST databases of tomato. Their orthologs were identified from tobacco, potato, N. benthemiana, pepper, and petunia. Phylogenetic analysis of AtGH3, SlGH3, and their Solanaceae orthologs provided insights into various orthologous relationships among these proteins. These genes were found to be responsive to a variety of signals including, phytohormones and environmental stresses. Analysis of AuxRE elements in their promoters showed variability in the sequence as well as number of this element. Up-regulation of only 11 SlGH3 genes, in response to exogenous auxin, suggested possible relationship between the diversity in the sequence and number of AuxRE element with the auxin inducibility. Expression analysis of SlGH3 genes in different vegetative and reproductive tissues/stages suggested limited or no role for most of the SlGH3 genes at the initiation of fruit ripening. However, up-regulation of SlGH3-1 and -2 at the onset of fruit ripening indicates that these genes could have a role in fruit ripening. The present study characterizes GH3 gene family of tomato and its evolutionary relationship with members of this family from other Solanaceae species and Arabidopsis. It could help in the identification of GH3 genes and revelation of their function during vegetative/reproductive development stages from other Solanaceae members.
Genome-wide analysis of auxin response factor (ARF) gene gamily from tomato and analysis of their role in flower and fruit development
(Springer Science, 2011) Kumar, Rahul; Tyagi, Akhilesh K.; Sharma, Arun K.
Auxin response transcription factors have been widely implicated in auxin-mediated responses during various developmental processes ranging from root and shoot development to flower and fruit development in plants. In order to use them for improvement of agronomic traits related to fruit, we need to have better understanding of their role during fruit development. In this study, 17 SlARF genes have been identified from tomato (Solanum lycopersicum), using various publically available tomato EST databases. Phylogenetic analysis of the 23 AtARF and 17 SlARF proteins results in formation of three major classes and a total of 14 sister pairs, including seven SlARF-AtARF, four SlARF-SlARF and three AtARF-AtARF sister pairs, providing insights into various orthologous relationships between AtARFs and SlARFs. Further, search for orthologs of these SlARFs resulted in identification of nine, ten, four and three ARF genes from potato, tobacco, N. benthemiana and pepper, respectively. A phylogenetic analysis of these genes, along with their orthologs from Solanaceae species, suggests the presence of a common set of the ARF genes in this family. Comparison of the expression of these SlARF genes in wild type and rin mutant provides an insight into their role during different stages of flower and fruit development. This study suggests that ARF genes may play diverse role during flower and fruit development. Comprehensive data generated here will provide a platform for identification of ARF genes and elucidation of their function during reproductive development stages in Solanaceae in general and fruit development in tomato, in particular.

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