Regulation of Arabidopsis Early Anther Development by Putative Cell‐Cell Signaling Molecules and Transcriptional Regulators

Abstract

Anther development in flowering plants involves the formation of several cell types, including the tapetal and pollen mother cells. The use of genetic and molecular tools has led to the identification and characterization of genes that are critical for normal cell division and differentiation in Arabidopsis early anther development. We review here several recent studies on these genes, including the demonstration that the putative receptor protein kinases BAM1 and BAM2 together play essential roles in the control of early cell division and differentiation. In addition, we discuss the hypothesis that BAM1/2 may form a positive-negative feedback regulatory loop with a previously identified key regulator, SPOROCYTELESS (also called NOZZLE), to control the balance between sporogenous and somatic cell types in the anther. Furthermore, we summarize the isolation and functional analysis of the DYSFUNCTIONAL TAPETUM1 (DYT1) gene in promoting proper tapetal cell differentiation. Our finding that DYT1 encodes a putative transcription factor of the bHLH family, as well as relevant expression analyses, strongly supports a model that DYT1 serves as a critical link between upstream factors and downstream target genes that are critical for normal tapetum development and function. These studies, together with other recently published works, indicate that cell-cell communication and transcriptional control are key processes essential for cell fate specification in anther development.Key words: anther development; Arabidopsis; signaling; tapetum; transcription factor. Available online at www.blackwell-synergy.com/links/toc/jipb, www.jipb.netIn flowering plants, reproduction depends on the production of pollen grains in the male reproductive organ called the anther.To produce pollen, several cell types must be formed during early anther development (Goldberg et al. 1993;Ma 2005). The progenitor of pollen is called the pollen mother cell, which undergoes meiosis to produce four microspores that develop into four pollen grains. At the time when the pollen mother cells are formed, the anther has four similarly shaped lobes, each of which has five cell types. On the surface is the epidermis, a cell layer that is derived from the L1 layer of the anther primordium. Interior of the epidermis is the endothecium, which surrounds the middle layer. Interior of the middle layer is the tapetum, which encircles the pollen mother cells and is known to be critical for pollen development from the microspore (Mariani et al. 1990;Goldberg et al. 1993;Ma 2005 Hord et al. (2006) showed that the BAM1 and BAM2 putative receptor-like protein kinases are critical for very early development of the Arabidopsis anther. BAM1 and BAM2 are closely related in sequence to the CLAVATA1 (CLV1) putative receptor-like protein kinase, which has been shown to be critical for the homeostasis of the stem cell pool in the shoot apical meristem (Clark et al. 1997). CLV1, BAM1, BAM2, and a fourth gene called BAM3, form a small clade with strong support Hord et al. 2...

Somatic and Reproductive Cell Development in Rice Anther Is Regulated by a Putative Glutaredoxin

“…It has always been supposed that signal transduction pathways contribute to the early anther cell differentiation, but what kinds of signal molecules are involved have not been identified (Sun et al, 2007). MIL1's glutaredoxin property, combined with the fact that redox modifications play significant roles in cell signaling, suggests MIL1 might influence male meiosis initiation via participation in an anther-specific meiosis initiation signaling pathway.…”

Analysis of anther transcriptomes to identify genes contributing to meiosis and male gametophyte development in rice

“…Development and release of mature pollen is dependent on the elaborate coordination of many genes expressed in both non-reproductive as well as reproductive cell layers of the anther. Thus, the anther is a multicellular organ that undergoes complex processes such as cell fate determination [2], cell differentiation, reductional division [3] and cell-cell communication [4]. …”

Regulatory Role of a Receptor-Like Kinase in Specifying Anther Cell Identity

“…The spl/nzz mutant has no formation of microsporocytes and anther somatic wall layers; this AGAMOUSregulated factor connects floral organ determination with the initiation of anther patterning (Schiefthaler et al, 1999;Yang et al, 1999). BAM1 (BARELY ANY MERISTEM1) and BAM2 encode CLAVATA1-related LRR-RLKs; BAM1/2 limit the expression domain of SPL/NZZ, and SPL/NZZ promotes BAM1 expression in the central sporogenous cells, contributing to the correct differentiation of the endothecium, SPC, and the resulting middle layers and tapetal layers Hord et al, 2006;Sun et al, 2007). ERECTA family genes ER (ERECTA), ERL1 (ERECTA-LIKE1), and ERL2, encoding the LRR-RLKs, redundantly control anther lobe formation and cell patterning (Torii et al, 1996;Shpak et al, 2003;Shpak et al, 2004;Woodward et al, 2005).…”