OsMFT2 is involved in the regulation of ABA signaling‐mediated seed germination through interacting with OsbZIP23/66/72 in rice

Abstract

Summary Seed germination is a complex process involving various physical and biochemical cues, determined by exogenous and endogenous factors. Here, we identified a gene, OsMFT2, that negatively regulates seed germination in rice. OsMFT2 knock‐out lines exhibited pre‐harvest sprouting, whereas OsMFT2 overexpression lines showed delayed germination. RNA expression profiling showed that OsMFT2 was specifically expressed in seeds. Subcellular localization indicated that OsMFT2 was a nuclear protein. Exogenous abscisic acid (ABA) treatment of imbibed seeds and seedlings indicated that OsMFT2 altered ABA sensitivity during seed germination and post‐germination growth. In vivo and in vitro assays showed that three bZIP transcription factors, OsbZIP23, OsbZIP66 and OsbZIP72, interacted with OsMFT2. OsbZIP23/66/72 bound to the promoter of Rab16A, a typical gene containing the ABA‐responsive element, and OsMFT2 enhanced the binding to the Rab16A promoter. Moreover, several ABA‐responsive genes were differentially expressed in the imbibed seeds of OsMFT2 transgenic lines and the wild type. The performance of the transgenic plants demonstrated that overexpressing OsbZIP23 rescued the pre‐harvest sprouting phenotype and the decrease in ABA‐signaling genes expression caused by OsMFT2 knock‐out. All of these results demonstrate that OsMFT2 positively regulates ABA‐responsive genes through interacting with OsbZIP23/66/72 and functions in seed germination.

Genome-Wide Identification and Expression Analysis of OsbZIP09 Target Genes in Rice Reveal Its Mechanism of Controlling Seed Germination

“…For example, mutation of OsABF2/SsbZIP46 decreased the sensitivity of rice to high levels of ABA at germination and post-germination growth stages [47]. OsbZIP23 directly interacts with MOTHER OF FT AND TFL 2 (OsMFT2), a negative regulator of rice seed germination, and OsbZIP23 overexpression restores the PHS phenotype of osmft2 knock-out lines [48]. Moreover, OsbZIP72 is activated by ABA and directly binds to the Allene Oxide Cyclase (AOC) promoter and enhances its transcription.…”

The Heat is On: How Crops Respond to High Temperature

“…In contrast, wheat grains matured under lower temperature (13degC) show an increased transcript level of MFT . In rice, OsMFT2 knock-out lines showed preharvest sprouting under high temperature and rainy weather, whereas wild type plants and overexpression lines did not (Song et al, 2020). In parallel, DOG1 transcript levels fluctuate according to both dormancy level and soil temperature in buried seeds, with low temperatures showing a higher level of DOG1 than high temperatures (Footitt, Douterelo-Soler, Clay, & Finch-Savage, 2011;Graeber et al, 2014;Nakabayashi et al, 2012).…”

Advances in the Identification of Quantitative Trait Loci and Genes Involved in Seed Vigor in Rice

“…Rice F-box protein OsFbx352 plays a regulatory role in the glucose-induced suppression of seed germination by targeting ABA metabolism, including ABA synthesis (OsNCED2 and OsNCED3) and ABA catabolism (OsABA-ox2 and OsABA-ox3), in the presence of glucose (Song et al, 2012). Rice mother of FT and TFL 1 (OsMFT2) negatively regulates seed germination, and it positively regulates ABA response genes through interacting with three bZIP transcription factors OsbZIP23/66/72 (Song et al, 2020). Several genes regulate seed vigor involved in the crosstalk between hormone and/or ROS pathways in rice (Figure 3).…”