| Most of rice leaf color mutant associated with chlorophyll synthesis,degradation,or chloroplast development,is a common type of mutation in nature,has the characteristics of obvious,easy to distinguish between recognizable characteristics.Chlorophyll plays an important role in photosynthesis,has the effects of photosynthetic energy capture and transmission.In rice,many chlorophyll deficient mutants could be divided into eight classes on the basis of their phenotypes,such as albino,green-white,yellow,light green,jade-white,greenish-yellow,olivine,stripe.It not only plays a crucial part in understanding plant chloroplasts structure,function,photosynthetic pigment synthesis,but also can be used as a marker in hybrid rice reproduction to miscellaneous the purity.We found a rice line 8272 which was imported from the United States in 2012 show its leaf tip gradually becoming yellow after a higher temperature(>30 ℃).The present thesis observed the agronomic traits and physiological characteristics,and by using molecular markers,gene mapping and candidate gene prediction was also carried out.The main results are as follows:1.Growing in natural condition of Nanjing or Hainan,when the highest temperature exceeds 30 ℃,leaf tip of 8272 from tillering stage appears as etiolation traits,and it was accompanied by the whole growth.When the highest temperature more than 35 ℃,the trait was shown more apparent,characterized by high temperature damage obviously.If the temperature was less than 28 ℃,the yellowing phenomenon was not obvious.Growing in an artificial climate box,the leaf chlorophyll content of 8272 showed decreased obviously(about 65.9%drop).2.Crossing 8272 with indica variety 9311 and japonica variety 02428 both which are with normal leaf color,reciprocal crosses of F1 was characterized by normal leaf color.In an F2 population of 8272/9311,leaf color of individual plant was separation,and the ratio of yellow plant vs green plants with a Mendel ratio of 1:3.Results showed that the yellow trait of 8272 under higher temperature were controlled by a pair of recessive nuclear genes.3.Using 8272/9311 F2 as the population for gene mapping,through the method of BSA,selecting 160 pairs of SSR primers to distinguish the polymorphism between 9311 and 8272,53 polymorphic markers were detected.Screening of construct polymorphism between 9311 and 8272,and two near isogenic pools from 8272/9311 F2 was carried out,and at the same time,more new primers is further synthesized.The gene was preliminary located on Chromosome 4 between RM16931 and RM16942,and the physical distance were 0.8cM and 3.3cM,respectively.Finally,the gene was mapped within a 117kb interval between RM16931 and InDel2.4.Determining the location of the primer RM 16931 and InDel2 in 9311 gene sequence,and an SNP differential screening analysis of 8272 and resequencing data was carried out in the primer interval,in which five genes were found to have a non-synonymous mutation SNP site.GO analysising for five candidate genes,the genes may cause the yellow character are sequenced.Sequencing found that a non-synonymous mutant SNP site between 9311 and 8272 in BGIOSGA015140,the SNP site(18029492)is A-C by a base mutation,the amino acid that leads to code is made from serine(Ser)to alanine(Ala).So the gene BGIOSGA015140 was presumed to be the candidate gene for the possible causing the yellow character.It may be related to the yellow phenomenon of 8272.The analysis was based on the data of Nipponbare and 9311,there are no reported leaf color gene in the range,so the mutant gene of 8272 might be a new gene for rice leaf color. |
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