MAP3Kε1/2 Interact with MOB1A/1B and Play Important Roles in Control of Pollen Germination through Crosstalk with JA Signaling in Arabidopsis

Restriction of pollen germination before the pollen grain is pollinated to stigma is essential for successful fertilization in angiosperms. However, the mechanisms underlying the process remain poorly understood. Here, we report functional characterization of the MAPKKK kinases, MAP3K epsilon 1 and MAP3K epsilon 2, involve in control of pollen germination in Arabidopsis. The two genes were expressed in different tissues with higher expression levels in the tricellular pollen grains. The map3k epsilon 1 map3k epsilon 2 double mutation caused abnormal callose accumulation, increasing level of JA and precocious pollen germination, resulting in significantly reduced seed set. Furthermore, the map3k epsilon 1 map3k epsilon 2 double mutations obviously upregulated the expression levels of genes in JA biosynthesis and signaling. The MAP3K epsilon 1/2 interacted with MOB1A/1B which shared homology with the core components of Hippo singling pathway in yeast. The Arabidopsis mob1a mob1b mutant also exhibited a similar phenotype of precocious pollen germination to that in map3k epsilon 1 map3k epsilon 2 mutants. Taken together, these results suggested that the MAP3K epsilon s interacted with MOB1s and played important role in restriction of the precocious pollen germination, possibly through crosstalk with JA signaling and influencing callose accumulation in Arabidopsis.

Automated summary

The study identified the importance of MAP3K epsilon 1 and MAP3K epsilon 2 kinases in controlling pollen germination in Arabidopsis, with double mutations leading to abnormal germination and reduced seed set. These genes interact with MOB1s and regulate precocious pollen germination by influencing JA signaling and callose accumulation.