DELLA-ARF/IAA Interaction Mediates Crosstalk between Gibberellin and Auxin Signaling in Controlling Fruit Initiation in Solanum lycopersicum

First author: Jianhong Hu; Affiliations: Duke Univeristy (杜克大学): Durham, USA

Corresponding author: Tai-ping Sun

Fruit initiation following fertilization (受精) in angiosperms is strictly regulated by phytohormones (植物激素). In tomato (Solanum lycopersicum), auxin and gibberellin (GA) play central roles in promoting fruit initiation. Without fertilization, elevated GA or auxin signaling can induce parthenocarpy 单性结实 (seedless fruit production). The GA-signaling repressor SlDELLA and auxin-signaling components SlIAA9 and SlARF7 repress parthenocarpy, but the underlying mechanism is unknown. Here, we show that SlDELLA and the SlARF7/SlIAA9 complex mediate crosstalk between GA and auxin pathways to regulate fruit initiation. Yeast-two-hybrid and co-immunoprecipitation assays (免疫共沉淀试验) showed that SlARF7 and additional activator SlARFs interact with SlDELLA and SlIAA9 through distinct domains. SlARF7/SlIAA9 and SlDELLA antagonistically (对抗性地) modulate the expression of feedback-regulated genes involved in GA and auxin metabolism, whereas SlARF7/SlIAA9 and SlDELLA co-regulate the expression of fruit growth-related genes. Analysis of procera (della), SlARF7 RNAi (with downregulated expression of multiple activator SlARFs), and entire (iaa9) single and double mutants indicated that these genes additively affect parthenocarpy, supporting the notion that the SlARFs/SlIAA9 and SlDELLA interaction plays an important role in regulating fruit initiation. Analysis of the GA-deficient mutant gib1 showed that active GA biosynthesis and signaling are required for auxin-induced fruit initiation. Our study reveals how direct crosstalk between auxin- and GA-signaling components is critical for tomato fruit initiation.

被子植物受精后的果实起始受到植物激素的严格调控。在番茄中，生长素和赤霉素GA在促进果实起始中发挥重要作用。在没有受精作用的情况下，提升GA和生长素信号可以诱导单性结实，即无核果实。GA信号抑制子SlDELLA和生长素信号组分SlIAA9和SlARF7能够抑制单性结实，但潜在的机制还不清楚。本文的研究显示SlDELLA和SlARF7/SlIAA9复合物介导GA和生长素通路的交联共同调控果实起始。酵母双杂和免疫共沉淀试验显示SlARF7和其他的SlARFs通过不同的结构域与SlDELLA及SlIAA9发生互作。SlARF7/SlIAA9与SlDELLA相互拮抗，调控参与GA和生长素代谢相关反馈调节基因的表达，而SlARF7/SlIAA9与SlDELLA共调控果实生长相关基因的表达。对于della突变体，SlARF7 RNAi干扰株及iaa9突变体的单突变和双突变研究显示这些基因呈加性影响番茄的单性结实。对于GA缺陷的gib1突变体研究表明有效的GA生物合成及信号对于生长素诱导的果实起始十分必要。本文的研究揭示了生长素与赤霉素信号通路直接的交联对于番茄果实起始的重要作用。

通讯：Tai-ping Sun (https://biology.duke.edu/people/tai-ping-sun)

个人简介：1980年，台湾国立清华大学，学士；1987年，杜克大学，博士。

研究方向：赤霉素通路调控植物生长发育的分子机制。

doi: https://doi.org/10.1105/tpc.18.00363

Journal: Plant Cell

First Published: 15 July, 2018

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