ORYZA SATIVA MYOSIN XI B controls pollen development by photoperiod-sensitive protein localizations

Myosins are actin-based motor proteins responsible for various motility and signal transduction. Only a small set of myosin classes is present inplants, and little is known about their functions. Here we showed how a rice myosin gene controlled pollen development by sensing changed environmental factors. The analysis is based on a gene-trapped Ds insertion mutant Oryza sativa myosin XI B (osmyoXIB). This mutant showed male sterility under short day length (SD) conditions and fertility under long day length (LD) conditions. Under both SD and LD conditions, the OSMYOXIB transcript was detected in whole anthers. However, under SD conditions, the OSMYOXIB-GUS fusion protein was localized only in the epidermal layer of anthers due to the lack of 3'-untranslated region (3'-UTR) and to dilute (DIL) domain sequences following the Ds insertion. As a result, mutant pollen development was affected, leading to male sterility. By contrast, under LD conditions, the fusion protein was localized normally in anthers. Despite normal localization, the protein was only partially functional due to the lack of DIL domain sequences, resulting in limited recovery of pollen fertility. This study also provides a case for a novel molecular aspect of gene expression, i.e., cell layer-specific translation in anthers.