Characterization And Functional Analysis Of QTL For Rice Flag Leaf Size And Plant Architecture

Improvement of plant architecture is an important approach to increase yield potential in rice.Flag leaf size and plant architecture are complex quantitative traits that are controlled by many loci with small effects.Chromosomal segment substitution line(CSSL)population,in which each line carries one or a few chromosomal segments from donor variety in a common background of the recipient variety,has been widely used for quantitative trait loci(QTL)identification and gene cloning.In the study,we identified several QTL for flag leaf length and width in the CSSL population,and cloned a candidate gene of the QTL controlls plant architecture.The main results are as follows:1.QTL for flag leaf length and flag leaf width in rice were detected with the CSSLpopulation with each line carrying one or a few chromosomal segments from theGeng/Japonica cultivar NIP in a common background of the Xian/Indica varietyZS97.In total,24 QTL for flag leaf length and 24 QTL for flag leaf width wereidentified,and explained 67.1%and 55.8%of the phenotypic variance of flag leaflength and width,respectively.2.One major QTL q FL7-2 for flag leaf length and width was delimited to a region of13.4 kb including Ghd7.1.Further,analysis of the natural allelic variation ofGhd7.1 and the mutants generated by CRISPR/Cas9 approach revealed thatGhd7.1 is the gene corresponding to the QTL(q FL7-2 or q FW7-2)for flag leafsize.3.Photosynthetic capacity in a pair wise NILs carrying the contrasting alleles of NIPand ZS97 at the NAL1 and Ghd7.1 loci were measured,and the results showedthat flag leaf size and photosynthetic parameters differ significantly between theNILs tested,the average values of transpiration rate were significantly higher inNIL-^NIP compared with NIL-^ZS97 of Ghd7.1.In contrast,between NILs of NAL1,NIL-^NIP reduced the photosynthetic rate relative to NIL-^ZS97.4.A QTL q PH8 for plant architecture was finely mapped to a 5 kb region.We identified a candidate gene for q PH8 by sequence comparison and expression analysis.q PH8 encodes a protein containing pectinesterase inhibitor domain.Gene expression analyses showed that q PH8 was constitutively expressed in root,stem and spikelets.Subcellular localization analyses revealed that q PH8 is located in the cell membrane.The pectin activity of NIL-^NIP significantly reduced compared with NIL-^ZS97,indicating that the degree of pectin methylesterification increased in NIL-^NIP.DNA methylation results indicated that q PH8 maybe regulated by DNA methylation.