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    Evolutionary and functional analysis of Two-Component System in chickpea reveals CaRR13, a TypeB RR, as positive regulator of symbiosis
    (John Wiley & Sons, 2021) Tiwari, Manish; Yadav, Manisha; Singh, Baljinder; Pandey, Vimal; Nawaz, Kashif; Bhatia, Sabhyata
    The critical role of cytokinin in early nodulation in legumes is well known. In our study, exogenous cytokinin application to roots of the important crop legume, chickpea (Cicer arietinum L.) led to the formation of pseudo nodules even in the absence of rhizobia. Hence a genome-wide analysis of the cytokinin signaling, Two-Component System (TCS) genes was conducted in chickpea, Medicago and Cajanus cajan. The integrated phylogenetic, evolutionary and expression analysis of the TCS genes was carried out which revealed that Histidine Kinases (HKs) were highly conserved, whereas, there was diversification leading to neofunctionalization at the level of Response Regulators (RRs) especially the TypeB RRs. Further, the functional role of the CaHKs in nodulation was established by complementation of the sln1Δ mutant of yeast and cre1 mutants of (Medicago) which led to restoration of the nodule deficient phenotype. Additionally, the highest expressing TypeB RR of chickpea, CaRR13 was functionally characterized. Its localization in the nucleus and its Y1H assay-based interaction with the promoter of the early nodulation gene CaNSP2 indicated its role as a transcription factor regulating early nodulation. Overexpression, RNAi lines and complementation of cre1 mutants with CaRR13 revealed its critical involvement as an important signaling molecule regulating early events of nodule organogenesis in chickpea.
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    High throughput identification of miRNAs reveal novel interacting targets regulating chickpea-rhizobia symbiosis
    (Elsevier B.V., 2021) Tiwari, Manish; Singh, Baljinder; Yadav, Manisha; Pandey, Vimal; Bhatia, Sabhyata
    Legumes developed symbiotic associations to meet its nitrogen requirement. The nitrogen fixation takes place in root nodules which involves bacterial colonization, organogenesis and nitrogen fixation. In order to unravel the miRNA mediated regulation of chickpea symbiosis, one microRNA and four parallel analysis of RNA ends (PARE) libraries were sequenced. Analysis of microRNA library identified a set of 91 miRNAs comprising of 84 conserved and 7 novel miRNAs. Additionally, PARE library analysis revealed 564 genes being targeted by 85 miRNAs. Phylogenetic analysis of the precursor sequences of the 91 miRNAs was carried out which revealed their ancestral relationships. Further, the mechanism of miRNAs biogenesis was predicted using the miRNAs information from other legumes. Reads from the nodule library were mapped to bacterial genomes to predict bacterial-encoded small RNAs. Real time expression analysis was used to validate the antagonistic expression pattern of important miRNA-mRNA target pairs. Four candidate miRNAs were selected for in planta study based on the antagonistic expression profiling as well as the novelty of their respective targets. miR171f, miR172c, miR394 and miR1509 targeted nodulation receptor kinase, Apetala2, histidine phosphotransferase, adenylate kinase respectively and were ectopically expressed in chickpea roots. The overexpression lines showed significant change in nodule numbers, the miR172c, miR394 and miR1509 resulted in an increase in nodule number whereas, miR171f overexpression led to a decrease in nodule number. Our analysis lays the foundation for functional characterization of novel miRNAs and their respective target pairs which control nodulation in chickpea and other leguminous crops.