The maize heterotrimeric G protein β subunit controls shoot meristem development and immune responses

First author: Qingyu Wu; Affiliations: Cold Spring Harbor Laboratory (冷泉港实验室): NY, USA

Corresponding author: David Jackson

Heterotrimeric G proteins are important transducers of receptor signaling, functioning in plants with CLAVATA receptors in controlling shoot meristem size and with pathogen-associated molecular pattern receptors in basal immunity. However, whether specific members of the heterotrimeric complex potentiate cross-talk between development and defense, and the extent to which these functions are conserved across species, have not yet been addressed. Here we used CRISPR/Cas9 to knock out the maize G protein β subunit gene (Gβ) and found that the mutants are lethal, differing from those in Arabidopsis, in which homologous mutants have normal growth and fertility. We show that lethality is caused not by a specific developmental arrest, but by autoimmunity. We used a genetic diversity screen to suppress the lethal Gβ phenotype and also identified a maize Gβ allele with weak autoimmune responses but strong development phenotypes. Using these tools, we show that Gβ controls meristem size in maize, acting epistatically with G protein α subunit gene (Gα), suggesting that Gβ and Gα function in a common signaling complex. Furthermore, we used an association study to show that natural variation in Gβ influences maize kernel row number, an important agronomic trait. Our results demonstrate the dual role of Gβ in immunity and development in a cereal crop and suggest that it functions in cross-talk between these competing signaling networks. Therefore, modification of Gβ has the potential to optimize the trade-off between growth and defense signaling to improve agronomic production.

异三聚体G蛋白是重要的受体信号转导分子，在植物中和CLAVATA受体一起作用于茎尖分生组织的大小，也能够与病原相关的分子模式受体一起作用于基础免疫。然而，有关异三聚体复合物中是否存在特定成员作用于增强发育与防御之间的交联，以及这些功能在物种间的保守程度这些问题都还不清楚。本文中，作者利用CRISPR/Cas9敲除了玉米中G蛋白的β亚基基因Gβ，结果发现该突变体是致死的，与拟南芥中的发现不同，拟南芥中Gβ的功能缺失突变体有着正常的生长和育性表型。作者发现玉米中Gβ突变体的致死表型并不是由于一个特定的发育缺陷所导致的，而是由于自身免疫导致的。作者利用遗传多样性筛选来阻止Gβ突变体的致死表型，同时作者鉴定到了一个玉米Gβ等位基因，该基因具有较弱的自免疫响应，但是具有较强的发育表型。利用这些工具，作者的研究显示Gβ基因控制玉米中分生组织的大小，与G蛋白α亚基基因Gα存在上位性效应，说明Gβ和Gα在一个共同的信号复合物中发挥作用。此外，作者利用一个关联研究发现Gβ基因中的自然变异会影响玉米一个重要农艺性状，即玉米仁的行数。本文的研究揭示了谷类作为玉米中Gβ基因作用于免疫和发育的双重作用，并且作用于这两个竞争信号网络的交联。因此，Gβ的修饰具有潜在的能力来最大化生长和防御信号之间的平衡，以提升农艺产量。

通讯：David Jackson (https://www.cshl.edu/research/faculty-staff/david-jackson/)

个人简介：1991年，英国约翰因内斯研究所，博士。

研究方向：调控植物生长和形状的基因和胞内信号。

doi: https://doi.org/10.1073/pnas.1917577116

Journal: PNAS

First Published: December 18, 2019