1The extra-ribosomal functions of ribosomal proteins RPL6 and RPL23a in stress-2 responsiveness have emanated from our previous studies on activation tagged mutants of rice 3 screened for water-use efficiency (Moin et al., 2016a). In the present study, we functionally 4 validated the RPL6, a Ribosomal Protein Large subunit member for salt stress tolerance in 5 rice. The overexpression of RPL6 resulted in tolerance to moderate (150 mM) to high (200 6 mM) levels of salt (NaCl) in rice. The transgenic rice plants expressing RPL6 constitutively 7 showed better phenotypic and physiological responses with high quantum efficiency, 8 accumulation of more chlorophyll and proline contents, and an overall increase in seed yield 9 compared with the wild type in salt stress treatments. An iTRAQ-based comparative 1 0 proteomic analysis revealed the high expression of about 333 proteins among the 4,378 DEPs

The Target of Rapamycin (TOR) protein kinase reprograms cellular metabolism under various environmental stresses. The overexpression of TOR in Arabidopsis resulted in increased plant growth including yield and biomass when compared with the wild type under both controlled and limited water conditions. In the present investigation, we report that Arabidopsis plants overexpressing TOR exhibited enhanced tolerance to the osmotic and salt stress treatments. Further to determine the role of TOR in abiotic stresses other than water limiting conditions, which were observed earlier in rice, we have treated high and medium TOR expressing Arabidopsis plants, ATR-1.4.27 and ATR-3.7.32 respectively, with stressinducing chemical agents such as Mannitol (100 mM), NaCl (150 mM), Sorbitol (200 mM) and PEG (7%). Both the lines, ATR-1.4.27 and ATR-3.7.32 exhibited enhanced tolerance to these stresses. These lines also had increased proline and total chlorophyll contents under stress conditions compared with their corresponding WT counterparts. The upregulation of several osmotic stress inducible genes in Arabidopsis transgenic lines indicated the role of TOR in modulating multi-stress tolerance. In the present investigation, we have also analyzed the transcriptional upregulation of ribosomal protein large and small subunit (RPL and RPS) genes in AtTOR overexpressing rice transgenic lines, TR-2.24 and TR-15.1 generated earlier (Bakshi et al., 2017a), which indicated that TOR also positively regulates the transcription of ribosomal proteins (RP) along with the synthesis of rRNAs. Also, the observations from phosphoproteomic analysis in SALK lines of various Arabidopsis T-DNA insertion mutants of ribosomal proteins showed differential regulation in phosphorylation of p70kDa ribosomal protein S6K1 and comparative analysis of phosphorylation sites for RSK (Ribosomal S6 Kinases) in RPL6, RPL18, RPL23, RPL24 and RPS28C proteins of Arabidopsis, Interestingly, rice showed similarity in their peptide sequences and Ser/Thr positions. These results suggest that the phosphorylation of S6K1 is controlled by loss/ inhibition of ribosomal protein function to switch 'on'/ 'off' the translational regulation for balanced growth and the pathways of both RPs and TOR are interlinked in a cyclic manner via phosphorylation of S6K1 as a modulatory step.

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