OsAID2 is required for the development of the secondary cell wall and for the elongation of the stamen filaments in rice anthers

초록

Plant reproduction involves complex developmental processes. Among them, anther dehiscence is a critical event in reproductive development leading to the release of pollen grains for pollination and fertilization. This event consists of several developmental steps, including tapetum degeneration, stamen filament elongation, lodicule swelling and the influence of phytohormones. Here, we report that Oryza sativa ANTHER INDEHISCENCE 2 (OsAID2) is involved in anther dehiscence and spikelet fertilization in rice. The osaid2 mutants exhibit pleiotropic phenotypes of altered flowering time, reduced tiller and spikelet number, abnormal floral organ development, and spikelet sterility under paddy field conditions. We found that the main cause of spikelet sterility in osaid2 is poor anther dehiscence rather than pollen viability through microscopic observations. OsAID2 is expressed at all stages of spikelet development and is particularly highly expressed in the developing anther, ovary and lodicule. In addition, we observed that the cause of anther indehiscence in the mutants is abnormal secondary cell wall formation in mature anthers as well as lack of stamen filament elongation. Chitin and cellulose accumulated more in the leaves of the mutant than in the wild type (WT). Semi-thin sections and scanning electron microscopy (SEM) showed that the secondary cell wall components were over-accumulated in the mutants compared to the wild type, resulting in impaired progression of anther dehiscence. We then found that the expression of OsGA2oxs, which degrades and reduces the bioactive gibberellin acid (GA), is highly increased in mature lodicules and anthers of the mutants compared to WT. This result suggests that stamen filament elongation is affected by reduced GA levels in the mutants. We are still investigating the further molecular function of OsAID2 in anther dehiscence and the role of this protein in the development of the secondary cell wall of the anther and the control