The protein kinase genes MAP3K ɛ 1 and MAP3K ɛ 2 are required for pollen viability in Arabidopsis thaliana

Abstract

SummaryWe have used reverse-genetic analysis to investigate the function of MAP3Ke1 and MAP3Ke2, a pair of closely related Arabidopsis thaliana genes that encode protein kinases. Plants homozygous for either map3ke1 or map3ke2 displayed no apparent mutant phenotype, whereas the double-mutant combination caused pollen lethality. Transmission of the double-mutant combination through the female gametophyte was normal. Tetrad analysis performed using the Arabidopsis quartet mutation demonstrated that the pollen-lethal phenotype segregated at meiosis with the map3ke1;map3ke2 genotype. We used transmission electron microscopy to determine that double-mutant pollen grains develop plasma membrane irregularities following pollen mitosis I. Analysis of the subcellular localization of a yellow fluorescent protein (YFP):MAP3Ke1 fusion protein using confocal microscopy and biochemical fractionation indicated that a substantial portion of the MAP3Ke1 present in Arabidopsis cells is localized to the plasma membrane. Taken together, our results suggest that MAP3Ke1 is required for the normal functioning of the plasma membrane in developing Arabidopsis pollen.

PIRL1 and PIRL9, encoding members of a novel plant-specific family of leucine-rich repeat proteins, are essential for differentiation of microspores into pollen

“…Similar male-specific gametophytic lethality has been observed for other Arabidopsis mutants, such as (for example) MAP3Ke knockout mutants (Chaiwongsar et al 2006) and the duo pollen mutants (Durbarry et al 2005). In fact, a large percentage of gametophyte mutants identified in forward screens were defective specifically in the male gametophyte (Boavida et al 2009;Procissi et al 2001;).…”

Plants, MEN and SIN

“…We are convinced that the plant SIN-like signaling pathways will provide new insights into plant cell differentiation. Data concerned with both the AtSGP GTPases by Bedhomme et al [5] and the AtMAP3Kepsilon kinases by Chaiwongsar et al [8] revealed two paralogues in Arabidopsis. Functional redundancy in plants introduces an additional level of complexity to the analysis of the SIN-like function [8].…”

“…The present number of paralogous genes encoding putative SIN-like elements in A. thaliana might have been reached through various mechanisms, including single gene duplications by short range duplication (AtMAP3Kepsilon1/2), or duplication of the whole genome through polyploidy (AtSGP1/2). Many knock-out mutants for A. thaliana duplicated genes resulting from recent polyploidisation, do not have phenotypical effect, as illustrated by independent T-DNA insertion mutants either for AtMAP3-Kepsilon1 or for AtMAP3Kepsilon2 [8]. The mechanism of compensation is putatively functional redundancy, i.e.…”

“…In a recent paper, Chaiwongsar et al [8] demonstrated that the AtMAP3Kepsilon function is different from the function of the yeast orthologue cdc7p in the SIN signaling pathway. Their results and our expression data rather suggest a function for the plant SIN-like module in the control of cell type specification [5].…”

Phytophthora infestans RXLR Effector PexRD2 Interacts with Host MAPKKKε to Suppress Plant Immune Signaling

“…Double loss-of-function mutations in MPK3 and MPK6 are embryonic lethal, and MPK4 mutants show a severely dwarfed phenotype (Wang et al, 2007;Qiu et al, 2008). Further upstream, double mutation of MAPKKKe1 and MAPKKKe2 in Arabidopsis is pollen-lethal, but plants containing individual mutations to MAPKKKe1 or MAPKKKe2 show no obvious phenotype (Chaiwongsar et al, 2006). The use of an inducible At-MAPKKKe1 construct in the mapkkke1 mapkkke2 background rescues pollen unviability, but the plants show reduced root length and reduced cell expansion in rosette leaves (Chaiwongsar et al, 2012).…”