Fine Mapping Of Source-sink-flow System Characters Of Ess1

Source, sink, transportation and the balance among them are important factors for rice yield. Thus, understanding of the molecular mechanism of the processes of source, sink, transportation and the ir banances will help us to breed rice with increased yield and elite quality. In recent years, many genes those regulate the size of leaf, spike and grain have been cloned via rice mutants. However, very few genes related to source, sink and transportation have been reported. Here, we report a rice natural mutant with multi-deficiencies in source, sink and transportation from rice Zhonghua-11 We named it early senescence 1(essl) as it exhibites early senescence. We studied this mutant essl using the strategies of phenotypic, microscopic, physiologic and molecular analyses, respectively. The main results obtained are summarized below. 1.Comparing to the wild type Zhonghua-11, we found that many changes in the mutant essl, such as, the height is decreased by 20.9%,the secondary branch number is decreased by 46.1%, the number of productive ears is decreased by 73.5%, the amount of spikehets is decreased by 87.5%, the length of first intermode is decreased by 19.5%; the 1000-rains weight is deceased by 18.1%, and the growth period of ess1 mutants longer than wild type about 8 days. Additionaly, we found that there are dificiencies in root growth and flower fertility of the mutant ess1.2. We observed the leaves and stems of the mutant ess1 and the wild type Zhonghua-11 by scanning electron microscopy and found that the vascular tissues of the mutant essl develop into malformation, which may lead to defects in transportation of water, inorganic salt and photosynthesis product. Moreover, we found some GOMs in the chloroplasts of the leaves from the mutant ess1 at the seedling stage, The amount of GOMs increased in the chloroplasts of the mutant ess1 at tillering and heading stage. In addition,there are some sap in chloroplast of ess1.3. We developed three F2 populations from the crosses of ess1XNip, ess1X9311, and ess1 X SH527, respectively, and performed genetic analysis. We found that the multitraits changes in the mutant ess1 was controlled by a single recessive gene.4.Using molecular markers, we mapped the gene Essl on the short arm close to the telomere of chromosome. Then we performed fine mapping using an amplified. F2 population with individuals derived from the cross of essl X 9311. We mapped and the gene Essl between the indel markers, InDe16 and InDel8, within 57.68kb of physical distance.5. We found that there are 9 genes annotated in the the region of 57.8 Kb in the reference genome of rice Nipponbarevia the website of Rice Genome Annotation Project. Out of the nine genes, LOC_Os05g48390 has been previously cloned as leaf tip necrosis 1 (ltnl) which plays a pivotal role in regulation of multiple phosphate starvation responses in rice. We cloned the gene LOC_Os05g4839 Oand found there is no any change of cDNA or genomic DNA sequences including the promoter and coding regions between the mutant essl and Zhonghua-11. We then found that the gene LOC_Os05g48360 encodes homologous protein to AT1G28380, of which the lose functional mutatation leads to a similar early senescence as the essl. Thus, we choosed the gene LOC_Os05g48360 as one of the most possible candidate genes of Essl. We analyzed the expression profile of the gene LOC_Os05g48360 and found that it is highly expressed in rice leaf and root.6. We selectively analyzed the expression of four SGRs genes in the mutant essl and wild type Zhonghua-11, and found that the expression of all four genes Os1295, Osl55, Osl20 and Osh69, respectively,is altered in the mutant essl compared with that in Zhonghua-11. The expression of these three genes Os1295, Os155, and Os120 is higher in the mutant essl than in Zhonghua-11 post emergence of early senescence of essl, whereas, the expression of Osh69 is higher in the mutant essl than in Zhonghua-11 before emergence of early senescence of essl. Thees results suggests that all four SGR genes, Os1295, Os155, Os120 and Osh69, are associated with early senescence of essl with that the Osh69 likely involved in the early stage of early senescence of the mutant essl.