Function Analysis Of Zinc-Finger Protein Gene Atsrz5 In Arabidopsis And Proteomic Analysis Of Salt Stress Treated Rice (Oryza Sative L.) Leaves

Post-transcriptional regulation of mRNA is an important pathway in the control of gene expression. RNA-binding proteins (RBPs) have been regarded as the primary regulators of mRNA stability and translation. More recently, it is shown that microRNAs can similarly affect mRNA stability and translation. RBPs and microRNAs can act synergistically to effect mRNA destabilization and translational inhibition. They can also engage in competition with each other and exert opposing effects on target mRNAs. Todate, several key studies in animals have provided critical evidence for the mechanisms of interaction between them, but the relative studies in plants were rarely reported.It was shown that the C2C2 (DWXCX1-4CX3NX6CX2C) type zinc finger protein Stress Repressive Zinc Finger Protein 5 (SRZ5) in Arabidopsis (Arabidopsis thaliala) isinvolvedin stress response and contains 3 ZnF (RanBP2-type zinc finger) motif. C2C2 type zinc finger proteins are widespread in plant. Five and four homologous proteins of SRZ5 exist in Arabidopsis and rice respectively. The proteins contain ZnF motif generally have the RNA binding activity. As the experiment shown, AtSRZ5 also had the activity of RNA binding and could bind the ARE (AU-Rich element) specifically.In additional, SRZ5 might plaied a role in the mRNA degradation mediated by miRNA for the interaction with AGO1 (Argonaute-1) in RISCs (RNA-induced silencing complex).AtSRZ5 participates in the stress response, and the deletion of AtSRZ5 reduced the sensitivity to salt-stress and ABA during the germination. With ABA treatment, the expression level of ABB(ABA insensitive3),ABI5 (ABA insensitive5), Eml (Late Embryogenesis Abundant 1) and Em6 (Late Embryogenesis Abundant 6) in srz5 was lower than that in WT (wild type). The expression of genes in Auxin signal pathway were also tested. GH3.3(Gretchen Hagen 3.3) was up regulated, and the degradation of ARF6(Auxin Response Factor 6)mRNA was repressed, while the degradation of ARF10(Auxin Response Factor 10) mRNA was promoted. AtSRZ5 affected the expression of ABI3 in ABA signal pathway through Auxin signal pathway.The sequence analysis of ARF6,ARF8,ARF10,ARF16and ARF17mRNAs shown that: 1. the degradations of ARF16and ARF17mRNA which contain no ARE were not changed in srz5;2. the degradations of ARF8and ARF10 mRNA which contain ARE in 3’UTR region were increased in srz5; 3. the degradation of ARF6 mRNA which contain ARE beyond 3’UTR region was decreased in srz5. The results indicated thecompetition and collaboration between SRZ5 and microRNAs, and the relationship was depended on the pattern of ARE.The level of ABI5 pre-mRNA first intron was higher in srz5 than that in WT. As the reports shown, the RBPs contained ZnF motif generally acted as the splicing regulators. Furthermore, several AREs were available in the first intron of ABI5 pre-mRNA. It was indicated that AtSRZ5 also acted as the splicing regulator.So, AtSRZ5 is a RBP which plays an important role in post-transcriptional regulation of mRNA, and the research could reveal the functions of the C2C2 type zinc-finger proteins in plant. Besides that, AtSRZ5 was induced by ABA and Axuin, and the study is a good evidence for the relationship among the plant hormones during the germination.The proteome of salt stress treated rice leaves was also analyzed by iTRAQ (isobaric Tags for Relative and Absolute Quantitation) in this paper.1,731 proteins were detected in rice leaves and the quantities of 56 of them were significantly altered. Among the 56 distinct proteins,43 of them were up-regulated and 13 of them were down regulated. The expressions of the coding genes were further analized by qRT-PCR (real-time quantitative reverse transcription PCR). It was found that those proteins were mainly classified in Oxidative Phosphorylation, Photosynthetic and Antioxidants.Based on the iTRAQ data, the expression pattern of the coding genes and the related studies, it was implied that,the antioxidants could regulate the PSI (photosystem I) and PSII (photosystem II) under the salt stress to control the ratio of ATP (Adenosine Triphosphate) andNADPH (Nicotinamide adenine dinucleotide 2-phosphate reduced), which would regulate the carbon fixation. Accompanying with the increased peroxiredoxin Q (PrxQ), the decreased thioredoxin M, thioredoxin peroxidase and GSTF3 (glutathione S-transferase F3) could down-regulate PSI subunit H (PsaH) and up-regulate PSI subunit D (PsaD) to control the cyclic electron flow and the generation of NADPH. The increased ATP and decreased NADPH in that progress could maintain the ratio of ATP/NADPH for the carbon fixation and prevent the overproduction of NADPH which would cause the generation of reactive oxygen species (ROS). The PrxQ also could protect PSII and maintain the ATP supply for the carbon fixation. Besides that, the limitation of carbon fixation would affect the energy supply for ionic regulation. In the salt stress response, the distinct proteins were connected to each other in the reprogramming of the rice leaves proteome.