Institutional Publications

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Author: search.filters.author.Singh, KirtiSubject: search.filters.subject.Arabidopsis

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    Phosphorylation of PIF3 by MPK6 is required for coordinated regulation of miRNA biogenesis and hypocotyl elongation in Arabidopsis
    (Elsevier B.V., 2023) Sharma, Deepika; Singh, Dhanraj; Singh, Kirti; Dwivedi, Aditi; Ranjan, Aashish; Sinha, Alok Krishna
    Light is one of the most important environmental factors that affect overall growth and development in plants. PHYTOCHROME INTERACTING FACTORs (PIFs) are negative regulators of photomorphogenesis. PIFs mediate light responses by interacting with downstream molecular partners and are essential regulators for hypocotyl elongation in Arabidopsis. Light induce activation of phytochromes (phys), promotes rapid phosphorylation, ubiquitination and degradation of PIFs. However the kinase responsible for the phosphorylation of PIFs and the signaling mechanism governing the adaptive changes leading to hypocotyl elongation to differential light intensities is not well understood. Here, we report interaction and phosphorylation of PIF3 by a mitogen-activated protein kinase 6 (MPK6) both in vitro and in vivo. Phosphorylation was significantly abolished when all the PIF3 putative phosphorylation sites were mutated to alanine. Further, we found that PIF3 directly binds to the bHLH binding domain in the promoter of RL responsive miRNA, miR163. Interestingly, phosphorylation status of PIF3 substantially affects the binding of PIF3 and mutated proteins to miR163 promoter. Further, overexpression of PIF3 affects the expression of red light (RL) responsive miRNAs and downstream genes involved in hypocotyl elongation and seedling development. These results suggest that MPK6-PIF3 module functions upstream of RL-responsive miRNAs and PIF3-regulated genes involved in photomorphogenesis, thus interconnecting these pathways together.
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    Arabidopsis MPK3 and MPK6 regulates D-Glucose signaling and interacts with G-Protein, RGS1
    (Elsevier B.V., 2022) Bhagat, Prakash Kumar; Sharma, Deepika; Verma, Deepanjali; Singh, Kirti; Sinha, Alok Krishna
    Sugar as a signaling molecule has attracted lots of attention. Even though several kinases have been shown to play a crucial role in the sugar signaling and response to exogenous D-glucose (Glc), the information on the involvement of MAP kinase cascade in sugar signaling has remain largely unexplored. In this report we demonstrate that MAP kinase signaling is essential for sensitivity to higher concentrations of D-Glc in Arabidopsis. We found that D-Glc activates MAP kinases, MPK3 and MPK6 in a concentration and time-dependent manner. The mutants of mpk3 and mpk6 display hyposensitivity to 6% D-Glc during seed germination, cotyledon greening and root growth. Interestingly, the altered sensitivity to increased D-Glc is severely enhanced by addition of 1% Sucrose in the media. Our study also deciphered the role of one of the Glc sensor proteins, RGS1 that interacts and gets phosphorylated at its C-terminal domain by MPK3 and MPK6. Overall our study provides a new insight on the involvement of MAP kinases in association with G-proteins that might regulate sugar signaling and sugar responsive growth and development in Arabidopsis.