The rice VCS1 is identified as a molecular tool to mark and visualize the vegetative cell of pollen

Cell-type-specific markers are valuable tools to reveal developmental processes underlying cell differentiation during plant reproduction. Here we report the pollen vegetative cell marker gene VCS1 (Vegetative Cell Specific 1) of rice (Oryza sativa japonica). VCS1 was expressed specifically in late pollen and was predicted to encode a small FAF domain-containing protein of 205 amino acid residues (aa). The expression of reporter fusion proteins showed that VCS1 was exclusively targeted to the vegetative nucleus of pollen. Upon pollen germination, VCS1 lost vegetative nucleus localization, and appeared diffused in the vegetative cytoplasm of pollen grain but not in the pollen tube. T-DNA insertional mutation which disrupted the carboxyl-terminal 21 aa of VCS1 did not affect plant vegetative growth and pollen development, while destruction of VCS1 by CRISPR/Cas9 only moderately affect pollen viability. VCS1 is evolutionally conserved in monocots but appeared absent in dicotyledons. This study reveals a molecular tool for visualizing the vegetative cell of rice and possible other monocots, which has potential values in the genetic engineering of male-sterile lines.细胞类型特异性标记物（cell-type-specific markers）是揭示植物生殖过程中细胞分化背后发育进程的宝贵工具。本研究报道了粳稻（Oryza sativa japonica）的花粉营养细胞特异性标记基因VCS1（Vegetative Cell Specific 1）。VCS1仅在发育后期的花粉中特异性表达，经预测其编码一种含FAF结构域（FAF domain）的小型蛋白质，共包含205个氨基酸残基（amino acid residues，简称aa）。报告融合蛋白（reporter fusion proteins）的表达实验显示，VCS1仅特异性定位于花粉的营养核中。花粉萌发后，VCS1不再保留营养核定位，而是弥散分布于花粉粒的营养细胞质内，却未出现在花粉管中。靶向破坏VCS1羧基末端21个氨基酸残基的T-DNA插入突变（T-DNA insertional mutation），并未影响植株的营养生长与花粉发育；而通过CRISPR/Cas9完全敲除VCS1，仅会对花粉活力产生轻度影响。VCS1在单子叶植物（monocots）中进化保守，但在双子叶植物（dicotyledons）中未检测到同源序列。本研究开发出一种可用于可视化水稻及其他可能的单子叶植物营养细胞的分子工具，在雄性不育系（male-sterile lines）的基因工程中具备潜在应用价值。