Institutional Publications

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Oryza coarctata PROTEIN L-ISOASPARTYL METHYLTRANSFERASE (PIMT) repairs isoaspartyl modification to antioxidative enzymes and is implicated in seed traits in rice
(Elsevier B.V., 2022) Kamble, Nitin Uttam; Petla, Bhanu Prakash; Ghosh, Shraboni; Achary, Rakesh Kumar; Majee, Manoj
PROTEIN L-ISOASPARTYL METHYLTRANSFERASE (PIMT) is a protein repairing enzyme, which is highly abundant in orthodox seeds, and plays an important role in seed vigor and longevity. PIMT essentially repairs isoaspartyl modification in proteins. Despite PIMT has been characterized from several orthodox seed producing plant species, role and regulation of PIMTs in recalcitrant seed producing plants are still limited. In the present study, PIMT from Oryza coarctata, which produces recalcitrant seeds and possess both enzymatically active (OcPIMT1–1 and OcPIMT2–1) and inactive (OcPIMT1–2 and OcPIMT2–2) PIMT isoforms, are functionally characterized through biochemical and genetic approach. We show that PIMT isoforms are differentially localized in Oryza sativa and Oryza coarctata. We also report that enzymatically active OcPIMTs isoforms, but not enzymatically inactive OcPIMTs isoforms, could impart seed vigor, viability and longevity in A. thaliana. Likewise, rice transgenic lines were also generated, and ectopic overexpression of enzymatically active OcPIMT isoforms resulted in increased seed length and weight with improved seed vigor and longevity. Subsequent analysis revealed that antioxidant enzymes (OsAPX and OsCAT) are susceptible to isoAsp modification, which negatively influences their biological functions; however, OcPIMTs physically interact, repairs and protect their function from harmful isoAsp modification, and thereby modulate ROS homeostasis in seeds during aging. Collectively, our results highlight the mechanisms and importance of ectopic expression of OcPIMT isoforms in seed desiccation tolerance and subsequent vigor, viability and longevity in rice.
A protein repairing enzyme, PROTEIN L- ISOASPARTYL METHYLTRANSFERASE is involved in salinity stress tolerance by increasing efficiency of ROS-scavenging enzymes
(Elsevier B.V., 2020) Ghosh, Shraboni; Kamble, Nitin Uttam; Majee, Manoj
Saline conditions can significantly affect plant growth and development, leading to massive reduction in crop yield. Herein, we show that a protein repairing enzyme PROTEIN L-ISOASPARTYL METHYLTRANSFERASE imparts salinity stress tolerance in Arabidopsis thaliana by repairing deleterious isoAsp accumulation during salinity stress. We demonstrate that salinity stress accelerates isoAsp accumulation in proteins and also induces PIMT activity in Arabidopsis. Transcript analysis indicates that both PIMT1 and PIMT2 are upregulated in response to salinity stress. Subsequent functional analysis reveals that PIMT1 and PIMT2 overexpression lines are tolerant, while RNAi lines are hyper sensitive to salinity stress in comparison to wild type (WT). Biochemical analyses of thesePIMT transgenic lines also reveals that compromised salinity tolerance of RNAi lines are linked to increased isoAsp accumulation, while improved tolerance of overexpression lines is associated with reduced isoAsp accumulation in proteins. Histochemical and biochemical studies further confirm lower accumulation of ROS and reduced lipid peroxidation in PIMT overexpression lines, while increased ROS accumulation and increased lipid peroxidation in RNAi lines as compared to WT under salinity stress. Interestingly, PIMToverexpression lines exhibit improved antioxidant enzyme efficiency, while RNAi lines display compromised antioxidant enzyme efficacy as compared to WT type plants. Our study suggests that PIMT improves salinity stress tolerance by restricting salt induced-excess ROS accumulation possibly by repairing isoAsp mediated protein damage of antioxidant enzymes. Our study can be utilized for enhancing salinity stress tolerance of economically important crops.
Stress inducible galactinol synthase of chickpea (CaGolS) implicates in heat and oxidative stress tolerance through reducing stress induced excessive reactive oxygen species accumulation
(Oxford University Press, 2018) Salvi, Prafull; Kamble, Nitin Uttam; Majee, Manoj
Raffinose Family Oligosaccharides (RFOs) participates in various aspects of plant physiology and galactinol synthase (GolS, EC 2.4.1.123) catalyzes the key step of RFO biosynthesis. Stress induced accumulation of RFOs particularly galactinol and raffinose has been reported in few plants; however their precise role and mechanistic insight in stress adaptation remain elusive. In present study, we have shown that the GolS activity as well as galactinol and raffinose content are significantly increased in response to various abiotic stresses in chickpea. Transcriptional analysis indicated that the CaGolS1 and CaGolS2 genes are induced in response to different abiotic stresses. Interestingly, heat and oxidative stress preferentially induce CaGolS1 over CaGolS2. Insilco analysis revealed several common yet distinct cis-acting regulatory elements in their 5' upstream regulatory sequences. Further, in vitro biochemical analysis revealed that CaGolS1 enzyme functions better in stressful conditions than CaGolS2 enzyme. Finally, Arabidopsis transgenic plants constitutively overexpressing CaGolS1 or CaGolS2 not only exhibits significantly increased galactinol but also raffinose content and display better growth responses than wild type or vector control plants when exposed to heat and oxidative stress. Further, improved tolerance of transgenic lines are associated with reduced accumulation of reactive oxygen species (ROS) and consequent lipid peroxidation as compared to control plants.Collectively, our data implies that GolS enzyme activity and consequent galactinol and raffinose content are significantly increased in response to stresses to mitigate stress induced growth inhibition by restricting excessive ROS accumulation and consequent lipid peroxidation in plants.

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