背景:导致花粉粒释放的花药裂开受多种因素的时空调控。在黄色羽扇豆(LupinusluteusL.)中,一个显示出cleistogamy的物种,花药在花开之前分裂,但是这个过程的过程和规律是未知的。花药发育的特定控制是通过激素途径进行的,其广泛的行动确保了生殖成功。在我们先前关于黄色羽扇豆中花和早期豆荚发育的研究中,我们表明,LLDELLA1的最低转录水平,赤霉素(GA)信号的主要阻遏物,大约在花药打开时发生;因此,这项研究的主要目的是精确研究赤霉素(GA3)对该物种花药开裂的依赖性调节。
结果:在本文中,我们显示了裂开过程中黄色羽扇豆花药结构的特定变化,包括通过木质纤维素沉积在内皮中的继发性增厚,隔膜/气孔处的酶促细胞壁分解和通过程序性细胞死亡(PCD)的细胞变性,并鉴定了几个与此过程广泛相关的基因。基因的表达谱随时间变化,在花药开放之前或开放时的阶段中mRNA积累最强烈。转录活性还揭示了这些基因以GA依赖性方式高度共表达和调节。GA3的细胞和组织定位表明,这些分子在花药打开之前就存在,主要在隔膜细胞中,在血管束附近和内皮中,并且它们随后无法检测到。GA3定位与GA生物合成和失活相关基因的转录活性密切相关。结果还表明GA3通过LlMIR159依赖性途径控制LlGAMYB表达。
结论:所呈现的结果表明,GA3在控制黄羽扇豆的广泛花药开裂过程中具有明显的贡献。了解在激素和分子水平上花粉释放的基础过程是控制这种经济上重要的豆类作物物种的育性的重要方面,并且越来越受到育种者的关注。
BACKGROUND: Anther dehiscence resulting in the release of pollen grains is tightly regulated in a spatiotemporal manner by various factors. In yellow lupine (Lupinus luteus L.), a species that shows cleistogamy, the anthers split before the flowers open, but the course and regulation of this process are unknown. The specific control of anther development takes place via hormonal pathways, the wide action of which ensures reproductive success. In our previous research concerning flower and early pod development in yellow lupine, we showed that the lowest transcript level of LlDELLA1, a main repressor of gibberellin (GA) signalling, occurs approximately at the time of anther opening; therefore, the main purpose of this study was to precisely investigate the gibberellic acid (GA3)-dependent regulation of the anther dehiscence in this species.
RESULTS: In this paper, we showed the specific changes in the yellow lupine anther structure during dehiscence, including secondary thickening in the endothecium by lignocellulosic deposition, enzymatic cell wall breakdown at the septum/stomium and cell degeneration via programmed cell death (PCD), and identified several genes widely associated with this process. The expression profile of genes varied over time, with the most intense mRNA accumulation in the phases prior to or at the time of anther opening. The transcriptional activity also revealed that these genes are highly coexpressed and regulated in a GA-dependent manner. The cellular and tissue localization of GA3 showed that these molecules are present before anther opening, mainly in septum cells, near the vascular bundle and in the endothecium, and that they are subsequently undetectable. GA3 localization strongly correlates with the transcriptional activity of genes related to GA biosynthesis and deactivation. The results also suggest that GA3 controls LlGAMYB expression via an LlMIR159-dependent pathway.
CONCLUSIONS: The presented results show a clear contribution of GA3 in the control of the extensive anther dehiscence process in yellow lupine. Understanding the processes underlying pollen release at the hormonal and molecular levels is a significant aspect of controlling fertility in this economically important legume crop species and is of increasing interest to breeders.