Death of female flower microsporocytes progresses independently of meiosis-like process and can be accelerated by specific transcripts in Asparagus officinalis

Abstract

Asparagus officinalis (garden asparagus) is a dioecious perennial crop, and the dioecy (i.e., sex) of A. officinalis can affect its productivity. In A. officinalis, flower anthers in female plants fail to accumulate callose around microsporocytes, fail to complete meiosis, and degenerate due to cell death. Although 13 genes have been implicated in the anther development of male and female flowers, it is unclear how these genes regulate the cell death in female flower anthers. The aim of this study was to narrow down factors involved in this process. TUNEL staining and Feulgen staining of female flower microsporocytes suggest that female microsporocytes enter a previously undetected meiosis-like process, and that the cell death occurs independently of this meiosis-like process, excluding the possibility that the cell death is caused by the cessation of meiosis. RNA sequencing with individual floral organs (tepals, pistils and stamens) revealed that several genes possibly regulating the cell death, such as metacaspase genes and a Bax inhibitor-1 gene, are differentially regulated between female and male flower anthers, and that genes involved in callose accumulation are up-regulated only in male flower anthers. These genes are likely involved in regulating the cell death in female flower anthers in A. officinalis.