The Role Of Sucrose Transporters OsSUT2 And OsSUT5 In Molecular Regulation Of Physiological Traits During Grain Filling Period In Transgenic Indica Rice (Oryza Sativa L.)

In this paper, we use three created transgenic indica rice lines(OsSUT5-OX, OsSUT5-antisense and OsSUT2-OX)to investigate the OsSUT5 and OsSUT2 roles in the regulation of grain filling via the detection on physiological, biochemical and molecular level , analysis of major agronomic traits and rice quality. The results are summarized as follows:1. The semi-quantitative RT-PCR shows that OsSUT5 is over expressed in the panicles of OsSUT5-OX lines at the grain-filling stage, OsSUT5 is repressed in the panicles of OsSUT5-antisense lines at the grain-filling stage. The OsSUT5 expression level is positively correlated with the gene expression level of OsSUT4, GBSS II, SSS I, Sus, SBE I.2. The detection of -2 leaf sheaths and leaves dry weight and non-structural carbohydrates content in -2 leaf sheaths and leaves demonstrates the over- expression of OsSUT5 promotes carbohydrate collection and carbon translocation from the sheaths to the panicles, while the repressed-expression of OsSUT5 contributes to the less carbohydrate collection and carbon translocation from the sheaths to the panicles.3. In the field observation of OsSUT5-OX lines and OsSUT5-antisense lines, we discovers that OsSUT5-OX lines flower two days earlier than wild line, OsSUT5-antisense lines flowers at least seven days later and more tillers than wild line. The observation of transgenic lines yield traits shows the over-expression of OsSUT5 increases setting rate, numbers of spikelet per panicle and main stem weight,while the repressed-expression of OsSUT5 leads to the decline of grain yield.4. The OsSUT5 influences the amylose content. The over-expression of OsSUT5 increases the amylose content, while repressed-expression of OsSUT5 decreases the amylose content.5. The semi-quantitative RT-PCR shows that OsSUT2 is over expressed in the panicles of OsSUT2-OX lines at the grain-filling stage, the OsSUT2 expression level is negatively correlated with the gene expression level of OsSUT4, GBSS II, SSS I, Sus, SBE I.6. The detection of -2 leaf sheaths and leaves dry weight and non-structural carbohydrates content in -2 leaf sheaths and leaves demonstrates the over- expression of OsSUT2 leads to less carbohydrate collection and carbon translocation from the sheaths to the panicles.7. The observation of transgenic lines yield traits shows the over-expression of OsSUT2 leads to decline of setting rate, numbers of spikelet per panicle and main stem weight, hence the grain yield of OsSUT2-OX lines decrease.In conclusion, OsSUT2 and OsSUT5 have different roles in the regulation of grain filling. The over-expressed OsSUT5 increases some grain-filling related genes expression level and promotes carbohydrate collection and carbon translocation from the sheaths to the panicles; besides, the over-expressed OsSUT5 increase the grain yield. Contracted with the negative effects of the OsSUT5-antisense lines, we could draw a conclusion that OsSUT5 is an important genes in grain filling regulation, it may associated with the start of grain filling. The over-expressed OsSUT2 leads to the decline of grain yield, then it suggests that OsSUT2 is a negative factor in the regulation of grain filling. The conclusion needs further study of OsSUT2-antisense lines.