Mitochondrial gene expression in stamens is differentially regulated during male gametogenesis in Arabidopsis

Abstract.

Patterns of mitochondrial (mt) gene expression in male reproductive tissues and the correlation of such gene expression with developmental events have been studied to a limited extent in only a few plant species. In the present paper, expression of the mitochondrial genes atp1 and cox3, coding for the α subunit of the F₁F₀ ATP synthase and subunit 3 of cytochrome oxidase, respectively, was characterized during stamen development in Arabidopsis by RNA gel blot and in situ hybridization. Two atp1 transcripts were seen, which showed organ-specific expression levels. In contrast, a single size class of cox3 transcript was found which showed an equal abundance in roots, leaves and flowers. Atp1 transcripts were detected in all tissues of pre-meiotic flower buds and were particularly abundant in pollen mother cells and in the tapetum during meiosis. However, no atp1 transcripts were detected in post-meiotic anthers. In contrast, cox3 transcripts were abundant in the tapetum of late meiotic and post-meiotic anthers and persisted until tapetal degeneration. The results demonstrate that the timing and cell-specificity of mt gene expression are differentially regulated during the development of stamens and pollen and may reflect a changing respiratory status of mitochondria during male gametophyte development.