Yuzhu Lu, Jia Zeng, Qiaoquan Liu.

Front Plant Sci.; 2022 Jan 11;12:786641.  doi: 10.3389/fpls.2021.786641.

Abstract

Rice Growth-Regulating Factors (GRFs) were originally identified to be gibberellin (GA)-induced, but the nature of GA induction has remained unknown because most reports thereafter focused on revealing their roles in growth-promoting activities. GRFs have the WRC (Trp, Arg, Cys) domain to target DNA and contain the QLQ (Gln, Leu, Gln) domain to interact with GRF-Interacting Factor (GIF), which recruits ATP-dependent DNA translocase Switch/Sucrose Non-fermenting (SWI/SNF) for chromatin remodeling. Both GRFs and GIFs exhibit transcriptional activities but GIFs lack a DNA-binding domain. So, GRFs act like a navigator in the GRF-GIF-SWI/SNF complex, determining when and where the complex should work on. The levels of most rice GRFs can be sensitively regulated by miR396, which responds to many developmental and environmental factors. Recent clues from several studies highlight the original question of how GRFs participate in GA signaling. DELLA (contain DELLA motif) protein plays dual roles in controlling the level of GRFs by regulating the level of miR396 and interacting with GRFs. Here we address the question of why this complex plays an essential role in controlling plant growth focusing on the action of GA signaling pivot, DELLA.

See: https://pubmed.ncbi.nlm.nih.gov/35087553/

Figure 1: Rice miR396-growth regulating factors (GRF)-GRF Interacting factor (GIF)- Switch/Sucrose Non-fermenting SWI/SNF module in gibrellin (GA) signaling. (A) GRF-GIF-SWI/SNF module promotes plant growth. DELLA is degraded in the presence of a higher level of GA at meristematic organs or under suitable conditions, then GRF interacts with GIF which recruits SWI/SNF to form a positive complex for promoting plant growth. (B) DELLA antagonizes GRF under adverse conditions. A higher level of DELLA mediated by a lower level of GA under adverse conditions interacts with GRF. The separation between GRF and GIF mediated by DELLA leads to inhibition of plant growth. (C) GRFs are induced by GA. At meristematic organs or under suitable conditions along with a higher level of GA, degraded DELLA leads to a lower miR396 level which in turn results in a higher level of GRFs mRNA for translating protein. (D) miR396 suppresses GRFs mRNA under stress. A higher level of DELLA mediated by lower GA under stresses interacts with OsIDD2 to promote the expression of miR396 which in turn knocks down GRFs mRNA.