Abstract
The ERECT PANICLE 3 gene of rice encodes a peptide that exhibits more than 50% sequence identity with the Arabidopsis F-box protein HAWAIIAN SKIRT (HWS). Ectopic expression of the Os02g15950 coding sequence, driven by the HWS (At3g61950) promoter, rescued the hws-1 flower phenotype in Arabidopsis confirming that EP3 is a functional orthologue of HWS. In addition to displaying an erect inflorescence phenotype, loss-of-function mutants of Os02g15950 exhibited a decrease in leaf photosynthetic capacity and stomatal conductance. Analysis of a range of physiological and anatomical features related to leaf photosynthesis revealed no alteration in Rubisco content and no notable changes in mesophyll size or arrangement. However, both ep3 mutant plants and transgenic lines that have a T-DNA insertion within the Os02g15950 (EP3) gene exhibit smaller stomatal guard cells compared with their wild-type controls. This anatomical characteristic may account for the observed decrease in leaf photosynthesis and provides evidence that EP3 plays a role in regulating stomatal guard cell development.
Highlights
Inflorescences of the erect panicle 3 mutant in rice remain upright throughout grain filling
The ERECT PANICLE 3 gene of rice encodes a peptide that exhibits more than 50% sequence identity with the Arabidopsis F-box protein HAWAIIAN SKIRT (HWS)
This anatomical characteristic may account for the observed decrease in leaf photosynthesis and provides evidence that EP3 plays a role in regulating stomatal guard cell development
Summary
Inflorescences of the erect panicle 3 (ep3) mutant in rice remain upright throughout grain filling. The hws-1 mutant is distinctive as its floral organs look as if they are attached to the developing silique throughout maturation and senescence. A detailed study of flower development has revealed that this is the consequence of the sepals being fused into a single whorl trapping the separated petals and anther filaments and preventing them from being shed (González-Carranza et al, 2007). Identification and characterization of the gene responsible for the mutant phenotype has revealed a 28 bp deletion in a gene encoding an F-box protein leading to the synthesis of a truncated HWS peptide (González-Carranza et al, 2007). Phenotypic studies of hws-1, and transgenic lines ectopically expressing HWS, have shown that the gene may regulate both the size of aerial organs and seeds (González-Carranza et al, 2007) and play a role in regulating stomatal distribution and aspects of chloroplast assembly (Z González-Carranza et al, unpublished data)
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