ArabidopsisDUO POLLEN3 Is a Key Regulator of Male Germline Development and Embryogenesis  

Abstract

Male germline development in angiosperms produces the pair of sperm cells required for double fertilization. A key regulator of this process in Arabidopsis thaliana is the male germline-specific transcription factor DUO POLLEN1 (DUO1) that coordinates germ cell division and gamete specification. Here, we uncover the role of DUO3, a nuclear protein that has a distinct, but overlapping role with DUO1 in male germline development. DUO3 is a conserved protein in land plants and is related to GON-4, a cell lineage regulator of gonadogenesis in Caenorhabditis elegans. Mutant duo3-1 germ cells either fail to divide or show a delay in division, and we show that, unlike DUO1, DUO3 promotes entry into mitosis independent of the G2/M regulator CYCB1;1. We also show that DUO3 is required for the expression of a subset of germline genes under DUO1 control and that like DUO1, DUO3 is essential for sperm cell specification and fertilization. Furthermore, we demonstrate an essential sporophytic role for DUO3 in cell division and embryo patterning. Our findings demonstrate essential developmental roles for DUO3 in cell cycle progression and cell specification in both gametophytic and sporophytic tissues.

An EAR-Dependent Regulatory Module Promotes Male Germ Cell Division and Sperm Fertility in Arabidopsis

“…Seeds of the ProHAP2:HAP2-eYFP marker line (von Besser et al, 2006) were kindly provided by Mark Johnson. Transgenic ProCYCB1;1: MDB-GFP, ProHTR10:H2B-GFP, and ProDUO1:CYCB1;1 lines have been described previously (Brownfield et al, 2009a(Brownfield et al, , 2009b.…”

“…We monitored CYCB1;1 expression in daz1 daz2 germ cells using a similar CYCB1;1 reporter, ProCYCB1;1:MDB-GFP, in which the CYCB1;1 promoter and N-terminal mitotic destruction box (MDB) are fused to GFP (Brownfield et al, 2009b). To mark germ cell nuclei and to distinguish premitotic and mitotic cells, we used a ProDUO1:H2B-tdTomato transgene since the DUO1 promoter is active in duo1 (Brownfield et al, 2009a) and in daz1 daz2 mutant germ cells (see below; Figure 7E).…”

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.…”

Cis-Regulatory Elements Determine Germline Specificity and Expression Level of an Isopentenyltransferase Gene in Sperm Cells of Arabidopsis

“…The highly conserved GCS1/ HAP2 gene encoding a secreted membrane protein is essential for fertilization in a myriad of other eukaryotes as well (Mori et al, 2006;von Besser et al, 2006;Liu et al, 2008). Additional male gamete-selective genes have been identified and characterized in lily and Arabidopsis (Engel et al, 2005;Okada et al, 2005aOkada et al, , 2005bBrownfield et al, 2009aBrownfield et al, , 2009b.…”

“…The rice homolog of AtGEX2, OsGEX2, also confers sperm cell expression (Cook and Thilmony, 2012). DUO POLLEN 1 (DUO1) encodes a MYB transcription factor that is expressed specifically in generative cell and sperm cells and serves a key regulatory function for generative cell division and sperm cell differentiation in Arabidopsis (Rotman et al, 2005;Brownfield et al, 2009a;Borg et al, 2011), whereas DUO3 functions to activate expression of target germline genes of DUO1 and is required for cell cycle progression, sperm cell specification, fertilization, and embryogenesis (Brownfield et al, 2009b). Male gamete-expressed histone variants have also been identified from lily (Lilium longiflorum) and Arabidopsis (Ingouff et al, 2007;Okada et al, 2005aOkada et al, , 2005b.…”