Dr. Alok Krishna Sinha’s group at National Institute of Plant Genome Research is interested to understand the signal transduction pathway mediated through mitogen activated protein kinase (MAPK) cascade in plants. The group is well recognized both in the country and abroad. Dr. Sinha joined the institute in November 2003 and since then his group has published several papers on various aspects of MAP kinases. His notable findings are on model monocot plant, rice and model eudicot, Arabidopsis. Some of his findings and publications are detailed below.
The group reported regulation of SUB1A1, gene known to give submergence tolerance to rice by MPK3 in a feed forward loop mechanism, a complete new regulation of submergence tolerance in rice. The group showed that MPK3 specifically gets activated under submergence condition and that its activation is SUB1A1 dependent. SUB1A1 not only physically interacts but is also a phosphorylation target of MPK3. The MPK3 silenced rice plants lost the typical stuntend phenotype of SUB1A1 harboring rice plants when immersed in water. The interesting findings was published in the Plant Cell (Singh and Sinha, 2016). The finding will povide a new handle to tackle submergence tolerance in rice plants.
Working on Arabidopsis Dr. Sinha’s group reported involvement of a cross talk between light signaling and MAP kinase cascade. The interesting finding has been published in the Plant Cell (Sethi et al 2014). The work showed that MKK3-MPK6 module of MAPK cascade is activated by blue light in a MYC2-dependent manner during Arabidopsisseedling development. MPK6 physically interacts and phosphorylates MYC2, which in turn binds to the promoter of MPK6 and regulates its expression in a feedback mechanism under blue light signaling. For the first time a connection between the MAP kinase cascade and light signalling was elucidated.
The major work of Dr. Sinha’s lab is deciphering the role of MAPK cascade in rice. The group reported identification of entire gene family of MAPK, MAPKK (Kumar et al 2008) and MAPKKK (Rao et al 2010) in rice. His group also reported existence of an internal rhythm in the activity of MAPK under the control of circadian rhythm (Rao et al 2009). They also identifed two MAPKs specifically activated in rice root and leaf upon arsenic treatment (Rao et al 2011). The possible MAPKK activating the arsenic activated MAPKs in rice root and leaf was also identified. One of the MAPKKs, OsMKK3 showing regulation under salinity stress was engineered into its constitutive active form. Transgenic rice plants overexpressing the constitutive active form of OsMKK3 showed tolerance towards salinity stress (Kumar et al 2013). Interestingly, the same transgenic plants showed increased accumulation of phytoalexins in rice under UV stress and Magnaporthae oryzaeinfection (Wankhede et al 2013). They also identified that OsMPK3 acts down stream to OsMKK3 under UV stress and that OsMPK3 targets OsWRKY39 for gene regulation. The group has also generated an protein-protein interactome map of rice MAPKs and MAPKKs (Wankhede et al. 2013).
In one of the pathbreaking finidngs, Dr. Sinha’s group for the first time reported protein-protein interaction between two MAP kinases in rice, a deviation form the canonical MAPK cascade (Sheikh et al 2013). The unique interaction, identified by yeast-two-hybrid assay was validated in-palnta by co-immunoprecipitation and FRET assays was found to boost the plant immunity. Recently the group reported that cytokinin producing Agrobacterium strain confers resistance against pathogen attack and that this resistance is achieved by activation of MAPK cascade (Sheikh et al. 2014). In one of the intersting findings the group reported the role of MAPKs, particularly MPK3 in miRNA biogenesis, both in rice and Arabidopsis (Raghuram et al 2014). It was shown that double stranded RNA binding proteins (DRBs) are phosphorylated by MPK3, which inturn inhibits its complex formation with DCL1 therby negatively regulating miRNA biogenesis. This finding opens up a complete new regulation of miRNA biogenesis in plants. More recently involvement of MAPK cascade in transducing rice pathogen, X. oryzaesignaling (Jalmi and Sinha, 2016). They showed a MAPK module consisting of MKK3-MPK7-WRKY30 involved in X. oryzaesigaling using series of molecular, biochemical and genetic studies.
Dr. Sinha’s group has also contributed in understanding mono-terpenoid indole alkaloid (MIA) pathway in Catharanthus roseus. The group identified a novle peroxidase gene, CrPRX1 probably playing important role in dimerization of catharanthine and vindoline to produce the precursor of economically importatnt alkaloids, vinblastine and vincristine (Kumar et al 2007, 2011; Jaggi et al 2011). They also produced several lines of hairy root cultures of C. roseusaccumulating high amount of alkaloids (Taneja et al. 2010). A novel MAP kinase, CrMPK3 was identified for the first time in C. roseusplaying important role in transducing stress signals resulting in higher accumulation of alkaloids (Raina et al 2012).
In all these years Dr. Sinha has also established national and international collaborations. He had a DST-DAAD programme with Prof. Thomas Roitsch, at Institute of Pharmaceutical Biology, University of Wuerzburg, Germany from 2007-2009. Very recently he had one of his students working under DAAD Sandwich program with Porf. Dierk Scheel, at Leibniz Institute of Plant Biochemistry, Halle, Germany from 2012-2014. Dr. Sinha is also running a successful SERB-DST collaborative project with Prof. Sudip Chattopadhyay, at Department of Biotechnology, NIT, Durgapur.