Genetic Analysis And Gene Mapping Of A Long Sterile Lemma Mutant Oslsl In Rice (Oryza Sativa L.)

The molecular mechanism of floral organ development has become a hot spot in plantdevelopmental biology. Recent studies have shown that the molecular mechanism ofthe regulation of the inner floral organs development is largely conserved betweenmonocots and dicots, but little is known regarding the molecular mechanismunderlying the development of the monocot-specific outer flower organs. Rice as amonocotyledonous model plant, the sterile lemmas are its unique floral organs. Amutant named Oslsl, with two long sterile lemmas, was discovered from an M2population of rice （Oryza sativa subspecies indica “168”） mutagenized with radiationof⁶⁰Co γ-ray. In this study, the mutant was indentified by the analysis of themorphology of floral organs and agronomic traits of the mutant, the genetic analysisand the molecular mapping of genes OsLSL, the prediction and the sequencing of thecandidate gene, and the expression analysis of candidate gene in the wild-type plants.The main results are as follows:（1）Compared with wild-type plants, the most obvious difference was developmentalabnormalities of sterile lemmas of the mutant Oslsl. Its length showed much longerthan the wild-type plants. We found the two sterile lemmas length reached the lengthof lemma/palea in most spikelets of the mutant, but occasionally the sterile lemmas onthe palea side reached the length of lemma/palea and the sterile lemmas on the lemmaside were not affected or were affected to a smaller extent in some spikelets of themutant.In addition, its flowering time advanced about two weeks, resulting in thereduction of height of plants, panicle length and grains per spike in matrue period.（2）The mutant Oslsl was crossed with indica varieties9311and Pei’ai64Srespectively. The hybrid F₁progency showed normal phenotype of sterile lemmas.The χ2testing for F2population showed that the segregation ratio of normal plants andmutant plants was3:1, conforming to the madeline genetic laws. Thus the mutantphenotype was controlled by single recessive nuclear gene, named OsLSL．（3） F2populations for mapping the gene OsLSL was constructed from a cross betweenthe Oslsl and261S. SSR molecular markers published in the rice database were used for molecular mapping of the gene OsLSL. Ultimately the OsLSL was finely mappedto a about35.7kb region between the markers RM3196and RM6663on the short armof chromosome7.（4）There were seven annotated genes located in the anchored region. One possiblecandidate gene LOC_Os07g04670was verified by sequencing and the result foundthat the47th base of the gene C（cytosine） converted to A（adenine）, leading totransfomation from the Ser（serine） codon（TCG） to a stop codon（TAG）, which wouldresult in premature termination during mRNA translation. Therefore we assumed thatthe gene LOC_Os07g04670was the gene OsLSL controling the develpment of sterilelemmas. We found the gene OsLSL was allelic with the reported genes G1and ELE.（5） The tissue expression of the predicted gene LOC_Os07g04670at the wild-typeplants was analysed by RT-PCR. The result showed that the expression of the geneLOC_Os07g04670in wild-type plants at the heading shortly was detected in leaves, leaf sheaths, panicles, stems and roots. The expression in leaves, leaf sheaths, stemsand roots was very low, but there was a strong expression in the developingpanicles. It further validated that the gene LOC_Os07g04670may play a role in theprocess of flower development.