AtMPK4 is required for male‐specific meiotic cytokinesis in Arabidopsis

Abstract

SUMMARYMitogen-activated protein kinase (MAPK) cascades have been implicated in regulating various aspects of plant development, including somatic cytokinesis. The evolution of expanded plant MAPK gene families has enabled the diversification of potential MAPK cascades, but functionally overlapping components are also well documented. Here we report that Arabidopsis MPK4, an MAPK that was previously described as a regulator of disease resistance, can interact with and be phosphorylated by the cytokinesis-related MAP kinase kinase, AtMKK6. In mpk4 mutant plants, anthers can develop normal microspore mother cells (MMCs) and peripheral supporting tissues, but the MMCs fail to form a normal intersporal callose wall after male meiosis, and thus cannot complete meiotic cytokinesis. Nevertheless, the multinucleate mpk4 microspores subsequently proceed through mitotic cytokinesis, resulting in enlarged mature pollen grains that possess increased sets of the tricellular structure. This pollen development phenotype is reminiscent of those observed in both atnack2/ tes/stud and anq1/mkk6 mutants, and protein-protein interaction analysis defines a putative signalling module linking AtNACK2/TES/STUD, AtANP3, AtMKK6 and AtMPK4 together as a cascade that facilitates male-specific meiotic cytokinesis in Arabidopsis.

Soybean Homologs of MPK4 Negatively Regulate Defense Responses and Positively Regulate Growth and Development

“…While MPK3 and MPK6 act as positive regulators of defense responses (Asai et al, 2002;Menke et al, 2005;Takahashi et al, 2007;Ren et al, 2008;Mao et al, 2011), MPK4 negatively regulates defense responses (Petersen et al, 2000;Brodersen et al, 2006;Gao et al, 2008). Besides its role in defense, MPK4 also plays a role in cytokinesis (Kosetsu et al, 2010;Beck et al, 2011;Zeng et al, 2011).…”

AtMKK6 and AtMPK13 are required for lateral root formation in Arabidopsis

“…11 Recently, AtMPK4 was demonstrated to serve as a target of AtMKK6 in processing somatic cytokinesis in the root, 12 as well as in male-specific meiotic cytokinesis. 1 By contrast, no cytokinesis defect was…”

“…In our recent publication, 1 we identified AtMPK4 as one of the downstream targets of AtMKK6 that is required for executing male-specific meiotic cytokinesis. Here we provide evidence that another target, AtMPK13, is developmentally co-expressed with AtMKK6 in Arabidopsis, and both AtMPK13 and AtMKK6 display high Promoter::GUS activity in the primary root tips and at the lateral root primordia.…”

“…12 However, two variants of the AtMPK13 mRNA are expressed in Arabidopsis and this insertion event disrupts only the long coding sequence (CDS) of AtMPK13, and not the short CDS. 1 Therefore, a clear picture of the biological function of the proposed AtMKK6-AtMPK13 cascade is still lacking.…”

“…Since the AtMKK6 knockout allele is severely stressed and sterile, and there is no null knockout allele of MPK13, 1 we generated dexamethasone (Dex)-inducible RNA interference lines for each kinase. Multiple independent T3 transgenic lines were selected that showed reduced accumulation of either AtMKK6 mRNA or AtMPK13 mRNA, respectively, 24 h after Dextreatment ( Fig.…”