Identification Of Arsenic-tolerant Contrasting Wild Rice Genotypes And Uncovering Their Underlying Different Mechanisms Of Arsenile Tolerance At The Whole Proteome-wide Level

The production and quality of rice, as well as human health are severely challenged bychronic exposure to arsenic (As) in rice. Improving the rice plants ability to As tolerance andreducing their absorption of As are demonstrated to be effective ways to solve the problem ofarsenic contamination in rice. As reported, there is significant genotypic difference among ricecultivars on arsenic uptake, transport and tolerance. However, how about the As tolerance for wildrice and the underlying molecular mechanisms are still remained unknown. As demonstrated, wildrice possesses much more excellent genes than the cultivated rice, which provides the valuablematerials for further theoretical study and practical usage in rice resistent breeding. In this study,using12wild rice genotypes as research materials, we have firstly identified two wild rice that isthe most tolerant and sensitive to arsenite, respectively, and further characterized these proteinsthat are significantly differentially expressed between the two contrasting genotypes by usingiTARQ. On these bases, the underlying mechanisms of difference in arsenite tolerance werefurther discussed. The main conclusions are as follows:(1) Two wild rice92606and103420was considered as arsenite-toleant and sensitivegenotypes, respectively, when comprehensively considering the test genotypes’ phenotype, rootelongation, as well as their ability in As uptake and transformation after6days treatment with25μM arsenite, Compared with the arsenic sensitive rice103420, the activities of someantioxidant enzymes including SOD, CAT and APX have extensively increased in the seedlingleaves of92606under arsenic stress conditions, indicating that the genotype92606can be adoptedto arsenite probably by increasing the activity of antioxidant enzymes in plants to alleviateoxidative damage caused by arsenic.(2) Using the iTRAQ technology, we have identified3272proteins from root tissues in92606and103420when treated with25μM arsenite. After6h As treatment, a total of172proteins thatare significantly differentially expressed in92606were identified by comparison with that in CK,of which there are82and90proteins being up-and down-regulated, respectively. Comparatively,107up-regulated and112down-regulated proteins were identified in103420. The results of GOenrichment analysis and KEGG pathway analysis showed that, these differentially expressed proteins are mainly involved in the biological processes, such as metabolism, defense response,oxidative stress, photosynthesis, protein synthesis, glycolysis and three carboxylic acid (TCA)cycle as well as the synthesis of amino acids, etc. Especially, the expression of those proteinsrelated to the oxidative phosphorylation, cysteine, glycine and other amino acid metabolism, fattyacid biosynthesis related, were significantly induced in92606plant roots.(3) Most of the identified differentially expressed proteins between92606and103420aredistinct with those that are responses to arsenate stress, suggestive of their different molecularmechanisms in responses to arsenite and arsenate in rice.(4) By searching the rice inserted mutant database termed OryGenesDB, we found that thereare inserted mutants for most of the identified significantly differentially expressed proteins (>3times). Of these mutants, only several with observed phenotypes recorded in different mutantdatabases, which displayed abnormal phenotypes including low fertility, dwarf or semi-dwarf, andleaf chlorosis, etc.The results presented here not only provide the useful clue, basal theory, and crucial genesfor rice improvements or molecular breeding, but may also deepen our insights into understandingthe differential molecular mechanisms of arsenic tolerance in rice genotypes.