Physiological And Molecular Mechanisms Of Oat In Response To Alkali Stress

Oats are an important cereal crop used as food,feed,and forage worldwide.They grow well even in some salinized and alkalized regions,and serve as a phytoremediation crop to ameliorate salinized and alkalized soils.For a long time,agriculture and ecological environment are threatened by the salinized and alkalized soils in the world.In them,stress effect of alkalized soils is even severer to plants,and more than half of the saline-alkaline soils are alkalized soils in the world.Tandem mass tag(TMT)-based proteomic,non-invasive micro-test technique,etc.were employed to elucidate physiological and molecular mechanism of oats in response to alkali stress by through examining several tissues of four varieties in different develop stages under alkali stress.Main results are as follow:Oats early seedlings were restrained significantly under low concentration alkali stress.The result showed that high pH was the main stress factor and its stress function was severer on oats than function produced by the low concentration ions(main Na+),which generate by "HCO3--CO32-" buffer system.In sodic soils,the balance of H+in cell,apoplast and rhizosphere were broken by high pH stress,and many H+transmembrane transporters were significant down-regulated expression.Other transporters assisted by H+were also down or up regulated expression.Many nitrate transporters(maximum up expression 2.9 folder),which transporting rely on H+assistant,and N assimilation enzymes were up-regulated expression significantly in roots.To further study,we found that translocation of nitrate and ammonia in resistance oats varieties were more efficient than sensitive oats varieties under alkali stress.Lots of Na+accumulated in tissues of oats under alkali stress,especially in roots;meanwhile,K+content decreased in these tissues clearly.The transmembrane transporters of P?Fe etc.also increased significantly.Under alkali stress,the synthesis process of photosynthesis pigments was restrained severely,and total content of these pigments declined clearly.Many Chlorophyllide a oxygenases were up-regulated expression(maximum up expression 8.3 folder,9.39 folder between two varieties' treatments),which catalyzed chlorophyll a converting into chlorophyll b to enlarge antenna molecular so to respond to the stress environment.Secondly,many PSI and PSII components proteins and pigments binding proteins were down-regulated expression,especially in sensitive oats varieties.Finally,during alkali stress,Ribulose-1,5-bisphosphate carboxylases were reduced significantly,but phosphoenolpyruvate carboxylases,mainly in roots of resistance oats varieties,were raised remarkably.Such changes wound help carbon fixation and net photosynthetic rate stability in resistance oats varieties,but changes in opposite trend lead to decline in sensitive varieties.Under alkali stress,protein synthesis was inhibited seriously,particularly in sensitive varieties,and a large of ribosome components and elongation factors were down-regulated expression in sensitive varieties.The result showed that small subunit ribosome protein S27e of leaves and large subunit ribosome protein L6?L7e of panicles were more sensitive to alkali stress.Many proteins in response to stress were up-regulated expression in cell and apoplast,for example,LEA,PRs,LTPs,and so on.Meanwhile,many proteins involving in expression regulation process and protein modification process raised significantly in resistance varieties panicles and in sensitive leaves.The second metabolism and amino acid metabolism were even more active.In panicles,there were more DEPs in sensitive varieties than resistance varieties under alkali stress.Lastly,Valine-Leucine-Isoleucine and Lysine degradation pathways were even more active in panicles.In summary,growth and development of oat roots were inhibited,oat roots'hairs were damaged,imbalance of H+in root cell were broken,uptake of N,K,P and Fe were decreased under high pH stress produced by "HCO3--CO32-" buffer system,combining with high concentration of Na+.Meanwhile,photosynthesis and protein synthesis system were inhibited severely,lots of resistance proteins produced.Kinds of key enzymes in N absorb process and assimilation,carbon fixation,photosynthesis components and proteins synthesis process can be as markers of alkali-resistance oat selection.