The final split: the regulation of anther dehiscence

Abstract

Controlling male fertility is an important goal for plant reproduction and selective breeding. Hybrid vigour results in superior growth rates and increased yields of hybrids compared with inbred lines; however, hybrid generation is costly and time consuming. A better understanding of anther development and pollen release will provide effective mechanisms for the control of male fertility and for hybrid generation. Male sterility is associated not only with the lack of viable pollen, but also with the failure of pollen release. In such instances a failure of anther dehiscence has the advantage that viable pollen is produced, which can be used for subsequent rescue of fertility. Anther dehiscence is a multistage process involving localized cellular differentiation and degeneration, combined with changes to the structure and water status of the anther to facilitate complete opening and pollen release. After microspore release the anther endothecium undergoes expansion and deposition of ligno-cellulosic secondary thickening. The septum separating the two locules is then enzymatically lysed and undergoes a programmed cell death-like breakdown. The stomium subsequently splits as a consequence of the stresses associated with pollen swelling and anther dehydration. The physical constraints imposed by the thickening in the endothecium limit expansion, placing additional stress on the anther, so as it dehydrates it opens and the pollen is released. Jasmonic acid has been shown to be a critical signal for dehiscence, although other hormones, particularly auxin, are also involved. The key regulators and physical constraints of anther dehiscence are discussed.

Temporal and spatial characteristics of male cone development inMetasequoia glyptostroboidesHu et Cheng

“…After enzymatic lysis of the septum, and the likely induction of programmed cell death, the septum ruptures to form a single locule and is followed by subsequent opening of the anther. 26 Although septum breakdown is absent in Ginkgo, the sporangium opens on the facing sides of two adjacent microsporangia, 25 which is similar to anther opening in angiosperms. However, in M. glyptostroboides, each microsporangium opens directly and independently along the dehiscence line.…”

“…25 In contrast, anther dehiscence in angiosperms has been studied extensively on a number of species, such as Arabidopsis, Lilium, rice, maize and members of the Solanaceae. 26 The basic processes of anther dehiscence in angiosperms are similar and involve secondary thickening in the anther endothecium, breakdown of the septum, splitting of the stomium and subsequent opening of the anther. 26 Results from the present study show that, during the development of the microsporangial wall and the process of microsporangium dehiscence, M. glyptostroboides displays the following two characteristics.…”

Identification and Dynamics of Arabidopsis Adaptor Protein-2 Complex and Its Involvement in Floral Organ Development

“…This appears to be the major cause of the observed reduction in fertility. The maturation of stamens involves cell elongation of the stamen filament, which synchronizes with development of the other floral organs to maximize the fertilization efficiency (Scott et al, 2004;Wilson et al, 2011). It is possible that AP-2 plays a role in filament cell elongation that requires cell wall biogenesis.…”

“…Mutations of genes involved in the biosynthesis and signaling of these phytohormones affect stamen filament elongation, anther dehiscence, and pollen viability. However, the molecular mechanisms underlying these effects are unknown (Scott et al, 2004;Wilson et al, 2011). AP-2 may play a role in clathrin-mediated endocytosis for the regulation of phytohormone signaling during floral organ development.…”

Transcription Factor MYB26 Is Key to Spatial Specificity in Anther Secondary Thickening Formation

“…This region subsequently defines the position of anther opening and does not develop the secondary thickening seen in the endothecium and connective tissues. Dehiscence is a two-phase process involving initial enzymatic degradation of the septum separating the two locules, followed by retraction of the locules resulting in a split at the stomium (Wilson et al, 2011). By a combination of molecular genetic analysis and mathematical modeling, we have shown that the mechanical control of opening is mediated by the bilayer structure of the mature anther wall (Nelson et al, 2012).…”