Characterization and Fine Mapping of SFL1, a Gene Controlling Screw Flag Leaf in Rice

Abstract

Leaf morphology of rice (Oryza sativa L.) is an important agronomic trait that greatly affects the total grain yield. In the present study, a mutant with screw flag leaf 1 (sfl1) was identified and characterized. The sfl1 mutants showed the screw flag leaf and panicle-at-bottom phenotype at reproductive stage, accompanied by a dramatic reduced plant height, flag leaf length and width, panicle length, and grain width. Histological analysis showed that the sfl1 mutant had increased small veins and number and size of bulliform cells compared with wild-type. Genetic analysis suggested that the mutant traits were completely controlled by a single recessive gene. The SFL1 gene was mapped to the long arm of chromosome 10 within a region of 49.7 kb between InDel markers B7P26 and B7P31. Cloning and sequencing results revealed that there was only one base substitution in the second exon of candidate gene Os10g0416200. The SFL1 locus encodes the 3-ketoacyl-CoA synthase 20 protein (KCS20). Furthermore, 288 KCS genes from 11 flowering plant species were identified using bioinformatics approaches. The qRT-PCR analysis showed that SFL1 was highly expressed in sheath, flag leaf and panicles. Furthermore, ROLLED and ERECT LEAF 2 (REL2), NARROW AND ROLLED LEAF 1 (NRL1), LEAF INCLINATION 2 (LC2), a zinc finger homeodomain class homeobox transcription factors gene (OsZHD1), ADAXIALIZED LEAF 1 (ADL1), ABAXIALLY CURLING LEAF 1 (ACL1), Rice outermost cell-specific gene 5 (Roc5), and ROLLED and ERECT LEAF 1 (REL1) were significantly upregulated while ROLLED LEAF 14 (RL14) was significantly downregulated in sfl1 mutant. These results provide an important basis for the functional analysis of SFL1 gene in rice leaf and panicle development, as well as exploration of further mechanisms controlling screw flag leaf trait for application in rice breeding.