Genetic Screening And Functional Analysis Of Genes For Morphogenesis Of Rice Lemma

Rice is one of the most important food crops in the world which provides nutrition supply for more than half of the population. Glume as an important rice floral organ, is mainly composed of palea and lemma. Both of them locate in the outer layer of the floral, provide nutrition for the seed development and protect the internal organs to avoid the intrusion of pests. More importantly, the size or the integrity of the glume will directly affect the yield and quality of rice. So the research in rice glume morphogenesis not only has the theoretical value but also has important practical application prospects. Our laboratory previously isolated a rice temperature-sensitive mutant, named osrdr6-1. The mutant shows temperature-dependent developmental defects in lemma. At high temperature (daily average temperature (DAT) is32℃), the lemma was severely affected, becoming a completely or partially radial, abaxialized awn-like structure; whereas the lemma develops normal at low temperature (DAT is28℃). Further studies confirmed that the lemma defects is caused by less accumulation of the small RNA, tasiR-ARFs in osrdr6-1, which results in up-regulation of its target genes, encoding auxin response factors2/3/4(ARF2/3/4).To explore the regulatory network on rice lemma morphogenesis, we adopt the genetics mutagenesis by EMS to screen the suppressors of lemma defects in osrdr6-1at high temperature. The M1seeds harvested by individual were planted at high temperature environment to screen. Totally,11suppressors were screened with completely or partially restoration of the osrdr6-1lemma defects and named hfl-hf11, respectively. This study is focused on hfl mutant to perform phenotype observation, genetic analysis, gene mapping and some functional analysis. The main results are as follows: 1, By morphological observation, we found that the hfl shows normal lemma at high temperature, but the anther is still shrinkage and infertile.2, By phenotype analysis of BC2F2population with hfl backcrossing osrdr6-1at the high temperature,72individuals showed restoration of lemma defect in a total of348F2population. The separation ratio is3:1(χ20,05,1=3.84), indicating that the phenotype is controlled by a pair of recessive gene.3, Using map-based cloning method to analysis the F2population with crossing by BC2F2(hf1) and Long Trapp B, the mutation site locates eventually is identified at a distance about5cM of chromosome1between markers RM7075and RM7192.4, Northern blot analyses showed that,tasiR-ARF accumulation is increased in hfl compared with osrdr6-1; the expression of three target mRNAs in hfl is lower than osrdr6-1,suggesting that hfl may be a positive regulatory factor for ARFs gene.