Cross Inhibition of MPK10 and WRKY10 Participating in the Growth of Endosperm in Arabidopsis thaliana.

Xiaoyuan Xi,Hao Xu,Zhengdao Hu,Xuerui Nie,Jing Li,Mingming Meng

doi:10.3389/fpls.2021.640346

Xiaoyuan Xi, Hao Xu + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2021.640346

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Abstract

The product of double fertilization produces seed, which contains three components: triploid endosperm, diploid embryo, and maternal seed coat. Amongst them, the endosperm plays a crucial role in coordinating seed growth. Mitogen-activated protein kinase (MAPK) cascades are conserved in eukaryotes and involved in signal transduction of plant development. MPK3, MPK6, and MPK10 form a small group of MPKs family in Arabidopsis thaliana. MPK3 and MPK6 are extensively studied and were found to be involved in diverse processes including plant reproduction. However, less is known about the function of MPK10. Here, we found WRKY10/MINI3, a member of HAIKU (IKU) pathway engaging in endosperm development, and MPK10 is high-specifically expressed in the early developmental endosperm but with opposite gradients. We further proved that MPK10 and WRKY10 cross-inhibit the expression of each other. The inhibition effect of MPK10 on gene expression of WRKY10 and the downstream targets is supported by the fact that MPK10 interacts with WRKY10 and suppresses the transcriptional activity of WRKY10. Constantly, mpk10 mutants produce big seeds while WRKY10/MINI3 positively regulate seed growth. Altogether, our data provides a model of WRKY10 and MPK10 regulating endosperm development with a unique cross inhibitory mechanism.

Highlights

Successful double fertilization in flowering plants produces seed
After sperms are released in the embryo sac, one sperm cell fuses with a haploid egg cell developing into a diploid embryo, and the other sperm cell fuses with a homodiploid central cell to form a triploid endosperm
A gradient expression pattern of MPK10 in endosperm showed by Clover signal could be clearly observed, which is low in the micropylar region and high in the chalazal region of endosperm (Figure 2A)

Summary

Introduction

Successful double fertilization in flowering plants produces seed. The seed is initiated from double fertilization events, which take place in the embryo sac, the female gametophyte of flowering plants (Faure, 2001). Egg cell and central cell, are contained in the embryo sac enclosed in the ovary (Christensen et al, 1997). In the male gametophyte pollen grains, two sperms are delivered to the embryo sac by a polar growth of pollen tube. After sperms are released in the embryo sac, one sperm cell fuses with a haploid egg cell developing into a diploid embryo, and the other sperm cell fuses with a homodiploid central cell to form a triploid endosperm. The endosperm has an essential function, like the mammal placenta, supplying nutrients to the embryo

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