On October 1, Current Biology published online the latest findings of Prof. Zhang Mengxiang’s team from College of Life Sciences, Wuhan University. The research reveals a novel molecular mechanism responsible for structural patterning and functional specifying the fine architecture of apical gynoecium.

The paper is entitled Three STIGMA AND STYLE STYLISTs Pattern the Fine Architectures of Apical Gynoecium and Are Critical for Male Gametophyte-pistil Interaction. The two co-first authors are Dr. Li Wenwei and Dr. Huang Xiaorong . The two co-corresponding authors are Prof. Zhang Mengxiang and A.P. Peng Xiongbo. The study was supported by the National Natural Science Foundation of China and the China Postdoctoral Science Foundation.

The gynoecium is derived from the fusion of carpels which, through adaptive adjustment in cell type and tissue distribution, evolves to facilitate efficient sexual reproduction. The apical gynoecium differentiates into a stigma and a style, both of which interact with male gametophyte, and is significant for plant fertility. However, how the fine structures of the apical gynoecium are established at the interface interacting with pollen and pollen tubes remains to be explained.

The study first reported a novel angiosperm-specific gene family, STIGMA AND STYLE STYLIST(SSS). By geno replication, SSSs evolve from a single copy within basal angiosperms such as Amborella trichopoda to a multi-member gene family. The family is composed of SSS1、SSS2 and SSS3 in Arabidopsis thaliana, all of which are preferential expressed respectively in the transmitting tract tissue of style, ground tissue of stigma and style, thus cooperatively controlling the structural patterning of apical gynoecium. SSSs cooperate in a dose-dependent manner, coregulating the patterning of the apical gynoecium via controlling cell expansion or elongation. Pollen tubes grow through the stylar tissues. The micro-environment the stylar tissues form interacts with pollen tubes and provides necessary nourishment for pollen tubes. SSSs’ functional defects will interfere with the normal growth of pollen tubes at the interface of pistil, which embodies in pollen tube growth slows and failures in passing through styles. This indicates that the fine architectures of apical gynoecium SSSs regulate is critical for male gametophyte-pistil interaction. Therefore, this work reveals that the volume control of cell number and the fine architectures of female reproductive organs are significant for the formation of adaptive mechanical structure and favorable microenvironment for communication with pistil to perform specific functions.

The author's further experiments showed that SSS genes are located at the downstream pollen tube growth pathway in the apical gynoecium. Previous studies have demonstrated that NGATHA can interact with TOPLESS and perform transcriptional inhibition. The expression of SSS genes in the down-regulated expression lines (amiR -NGA) and up-regulated expression lines (ANT>>NGA3) in this study down-regulate and up-regulate accordingly. These results indicate that NGA3 can also regulate SSS genes as activators, suggesting that NGA3 have diverse functions in different pathways of plant development. In brief, the NGA-SSS molecular regulatory pathway may be a conserved mechanism for angiosperms to regulate pistillate apical differentiation and fine style construction. It’s reported that this paper is another important research finding published in international journals by Sun Mengxiang's research group following their articles published in Nature Communications (2 papers)、 Dev Cell and Autophagy.

Article Link:

https://www.sciencedirect.com/science/article/pii/S0960982220313373

Written by Yang Xue

Rewritten by Wang Xuanqi

Edited by Shi Shang & Hu Sijia