Phenotype Identification And Gene Mapping Of A Rice Spikelet Development Mutant

Rice is one of the most important food crops in the world.Increasing rice yield and quality can effectively solve global food problems.Flower organ traits and formation process are the most direct related factors for rice yield.The research and application of genes related to floral organ development can help increase rice yield and quality.Through the in-depth study of the dicotyledonous model plants such as Arabidopsis thaliana and snapdragon,a classic ABC model of flower organ development regulation was formed.With the deepening research and more control genes be discovered,ABCDE model has been gradually developed.Combining the floral organ characteristics of monocotyledonous plants,it is generally believed that the floral organ development of rice is more in line with the ABCE model.In our laboratory,a stably hereditary spikelet development mutant was found in the breeding progeny of a breeding population,Shuhui 881/Yihui 1577.The phenotype of the mutant are mainly cannot closing,multiple glumes,and lodicules developed as glumes or conifers,or number and morphology of pistil and stamens.In this paper,systematic phenotype identification,genetic analysis and gene mapping of mutants were performed.The main results are as follows:1.Multiple phenotypic traits of the development mutant showed abnormalities during the spikelet’s development,such as multiple glumes,the glumes cannot closing,the inner flower organ entire exposed,lodicules developed as glumes or conifers,the number of stamens decreased,the number of pistils increased,the seed deformity and the rate of settling has dropped significantly,etc.2.Mutant phenotype began to emerge from segregation period of sepal primordium,and the segregation of pistil and stamen primordia was also severely affected by the mutant gene.Observations by scanning electron microscopy showed that the mutants showed normal from Primary branch primordium segregation to empty glume primordium segregation.The mutant phenotype began to appear when the primordium of sepals segregation,and the number of stamen primordium,pistil primordium,the type of double lemma were also different in the differentiation of pistil and stamen primordiums.Scanning electron microscopy was performed on the surface of the pistil and stamens and the surface of the sepals of the mutant phenotype and it was found that there was no significant difference between them.Semi-thin sections were made and cross sections of the rice glumes were observed.The mutations had multiple bracts and the lemma and palea were not hooked.3.Genetic analysis showed that the mutant phenotype was controlled by a pair of recessive single genes.A total of 4201 F₂segregating populations,including 3188normal phenotype plants,and 1013 mutant phenotype plants were established using the mutant and wild-type phenotype indica 9311.Theχ²test,which was in accordance with the trait separation ratio of 3:1,indicate that the mutant phenotype is controlled by a pair of recessive single genes.4.The gene was located on chromosome 3 between RM14772 and RM14784,with a physical distance of 273.6 kb.Firstly,this gene was mapped to chromosome 3 near RM569 by differential marker screening,linkage analysis,and genetic mapping.Then,chromosome walking was performed using a cryptographic marker.The gene was finally finely mapped between RM14772 and RM14784,the physical distance in this area is 273.6kb.5.LOC＿Os03g17920 was identified as a candidate gene of the mutant.Firstly,through on-line prediction,40 prediction genes were included in the positioning interval,and then only three candidate genes such as LOC＿Os03g17920,LOC＿Os03g17970,and LOC＿Os03g18140 existed candidate mutation sites by BSA morphological sequencing.Flower organ expression prediction analysis showed that LOC＿Os03g17970 and LOC＿Os03g18140 were mainly expressed in reproductive organs such as seeds and stigma,and they were lower in young panicles,while LOC＿Os03g17920 had higher expression levels during the whole panicle development.Further analysis of the LOC＿Os03g17920 gene sequence revealed that the gene has an insertion mutation of G→GCGTCGTGCGCGC at the 512th base of the coding sequence,resulting in amino acid insertion and frame shift mutation,resulting in changes in the encoded protein sequence and three-dimensional conformation,which may be caused by Causes of mutant traits.Therefore,LOC＿Os03g17920 was determined as a candidate gene of the mutant.