Preliminary Study On Transcription Factor, OsMYB3, In Rice

Rice is one of the most important crops in the world.Its yield and quality are of great impotant for agro-economic and food security.Although rice yield and quality are mostly controlled genetically,they also influenced by environmental factors,such as light and temperature.However,the molecular mechanisms are kept unknown.To elucidate how temperature and/or light affecting rice quality,a high temperature responsive transcription factor OsMYB3 was isolated in our previous study.Here we further characterized this gene.OsMYB3 is universally expressed in most of the rice tissues,such as seedlings,leaves,inflorescences and seeds.The expression of this gene is relative high in the developing endosperm and germinating;,seeds.Further studies revealed that OsMYB3 shows 50%identity with the rhythms of central oscillator component OsCCA1 which is involved in circadian regulation in rice.Expression of OsMYB3 is transiently induced by light and oscillates with a circadian rhythm.The peak of its expression appears at dawn while the valley of its expression appears in the evening.The peak value is about 70 times more than the valley value.In addition to being suppressed by high temperature,the expression of OsMYB3 can be greatly induced by cold and salt stress.Bioinformatic data showed that there are several light,heat and cold responsive cis elements in the promoter of OsMYB3.All these results suggested that this novel MYB-related transcription factor,OsMYB3,involved in the stress response by integrating light and temperature signals.Now we have obtained many genetic materials of OsMYB3 gene by using reverse genetic methods,including knocking out(CRISPY/CAS9 lines),knocking down(RNAi)and over-expression lines.And such transgenic lines should be the valuable materials to investigate the OsMYB3 functions in the future.Moreover,we have done some work on molecular breeding to improve eating and cooking quality in rice.By utilizing dwarf gene and heterosis,rice production has been greatly improved in the past decades.Recently,a greater demand for high rice quality arises in China with the development of living standard.Zhehui7954(ZH7954)is an elite restorer line with high yield and strong combination ability for three-line indica hybrid rice production.However,the amylose content of ZH7954 is high(?25%)which results in poor eating and cooking quality.Improvement of rice quality of ZH7954 was hard to achieve by using traditional breeding strategies.In this study,a dominant molecular marker named PCR-AccI was developed based on the G/T SNP at the first intron splicing site of rice Wx gene which mainly determines the amylose biosynthesis in rice endosperm.GG is usually correlated with high AC while TT rice has low or intermediate AC.Here,93-11 an elite parental line with intermediate AC(?17%)and T-type Wx(called Wxb)was used as a donor.Four elite lines were obtained with intermediate AC but similar phenotype as ZH7954 by backcross and molecular marker associated selection.L2 and L9 were used for further analysis.Both of them have better eating and cooking quality than receptor line ZH7954 while the appearance quality,such as grain shape,chalkiness,and grain weight are almost identical to ZH7954.These results suggested that the quality of ZH7954 was successfully improved by using molecular marker associated selection.Analysis data from SNP-typing showed that less than 7%of genome from 9311 was integrated to ZH7954 in both L2 and L9.The crop yield and combination ability will be further tested and such intermediate lines might be the valuable materials to generate elite restorer line with high yield and good quality in the future.