A Plant Germline-Specific Integrator of Sperm Specification and Cell Cycle Progression

Abstract

The unique double fertilisation mechanism in flowering plants depends upon a pair of functional sperm cells. During male gametogenesis, each haploid microspore undergoes an asymmetric division to produce a large, non-germline vegetative cell and a single germ cell that divides once to produce the sperm cell pair. Despite the importance of sperm cells in plant reproduction, relatively little is known about the molecular mechanisms controlling germ cell proliferation and specification. Here, we investigate the role of the Arabidopsis male germline-specific Myb protein DUO POLLEN1, DUO1, as a positive regulator of male germline development. We show that DUO1 is required for correct male germ cell differentiation including the expression of key genes required for fertilisation. DUO1 is also necessary for male germ cell division, and we show that DUO1 is required for the germline expression of the G2/M regulator AtCycB1;1 and that AtCycB1:1 can partially rescue defective germ cell division in duo1. We further show that the male germline-restricted expression of DUO1 depends upon positive promoter elements and not upon a proposed repressor binding site. Thus, DUO1 is a key regulator in the production of functional sperm cells in flowering plants that has a novel integrative role linking gametic cell specification and cell cycle progression.

MYB transcription factor genes as regulators for plant responses: an overview

“…AtMYB125/ DUO1 is a pollen-specific factor controlling male germ cell division and differentiation (Brownfield et al 2009). AtMYB33 and AtMYB65 redundantly facilitate both anther and pollen development (Millar and Gubler 2005).…”

Combinatorial interactions between LBD10 and LBD27 are essential for male gametophyte development in Arabidopsis

“…5 The R2R3 MYB transcription factor DUO1 and a nuclear protein DUO3 control proliferation of male germ line. 6,7 Analysis of lbd27 mutant indicated that LBD27 plays a role in the correct timing and orientation of the asymmetric microspore division. 8 Several LBD gene family members have been shown to play important roles in diverse aspects of lateral organ development in Arabidopsis, rice and maize.…”

A new role for plant R2R3-MYB transcription factors in cell cycle regulation

“…This year two papers reported a role of two members of this Arabidopsis subfamily in the regulation of the cell cycle. These are AtMYB59, which is involved in root growth [8] and DUO1 (AtMYB125), encoding a male germline-specific protein [9].…”

“…In another recent paper Brownfield et al showed that the Arabidopsis male germline-specific DUO1 gene, is required for correct male germline differentiation and for male germline cell division, controlling the expression of the G2/M regulator CYCB1;1 [9]. Expression of the cyclin B as a chimeric gene under the control of the DUO1 promoter can partially rescue defective germ cell division in the duo1 mutant.…”

“…Therefore the recent papers on AtMYB59 function in the root [8] and DUO1 role in the male germline [9] and the hypothesis of involvement of other R2R3MYB members in the local control of cell proliferation [7 and references therein] highlight that R2R3-MYB transcription factors also have a role in the regulation of the cell cycle. Probably in the near future a role in this process will be elucidated for other members of this large subfamily.…”