Coordinated Regulation of Gibberellin and Brassinosteroid Signalings Drives Toward a Sustainable “Green Revolution” by Breeding the New Generation of High-yield Wheat

doi:10.11983/CBB23038

Abstract

Abstract: Since the 1960s, the utilization of semi-dwarfing genes Rht-B1b and Rht-D1b has significantly improved the lodging resistance and harvest index of wheat (Triticum aestivum), leading to a doubling of global wheat production and triggering the “Green Revolution” in agriculture. Rht-B1b and Rht-D1b encode plant growth-inhibiting factors, DELLA proteins, which are negative regulatory factors in the gibberellin (GA) signaling pathway. Accumulation of DELLA proteins not only inhibits cell division and elongation, leading to a dwarf phenotype, but also suppresses photosynthesis and nitrogen use efficiency, resulting in semi-dwarf varieties requiring higher fertilizer inputs to achieve high yields. Addressing the challenge of “reducing fertilizer inputs while increasing efficiency” is a crucial issue for achieving green and low-carbon agriculture. Recently, Zhongfu Ni and his colleagues from China Agricultural University identified a novel “semi-dwarfing” regulatory module with potential breeding applications and demonstrated that reducing brassinosteroid (BR) signaling could enhance grain yield of wheat “Green Revolution” varieties (GRVs). They isolated and characterized a major QTL responsible for plant height and 1000-grain weight in wheat. Positional cloning and functional analysis revealed that this QTL was associated with a ~500 kb fragment deletion in the Heng597 genome, designated as r-e-z, which contains Rht-B1 and ZnF-B (encoding a RING E3 ligase). ZnF-B was found to positively regulate BR signaling by triggering the degradation of BR signaling repressor BRI1 Kinase Inhibitor (TaBKI1). Further experiments showed that deletion of ZnF-B not only caused the semi-dwarf phenotypes in the absence of Rht-B1b and Rht-D1b alleles, but also enhanced grain yield at low nitrogen fertilization levels. Thus, manipulation of GA and BR signaling provides a new breeding strategy to improve grain yield and nitrogen use efficiency of wheat GRVs without affecting beneficial semi-dwarfism, which will drive toward a new “Green Revolution” in wheat.

Key words: wheat, Green Revolution, plant height, gibberellin, brassinosteroid

Ming-Yi Bai, Jinrong Peng, Xiangdong Fu. Coordinated Regulation of Gibberellin and Brassinosteroid Signalings Drives Toward a Sustainable “Green Revolution” by Breeding the New Generation of High-yield Wheat[J]. Chinese Bulletin of Botany, 2023, 58(2): 194-198.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB23038

https://www.chinbullbotany.com/EN/Y2023/V58/I2/194

Figures/Tables 1

Figure 1 Schematic diagram of the “Green Revolution” Rht-B1-ZnF gene module regulating wheat important agronomic traits Rht-B1, a negative regulator of gibberellin (GA) signaling pathway, physically interacts with transcription factors GRF4 and BZR1 to inhibit their DNA binding ability. GA binding to the soluble receptor GID1 induces the degradation of Rht-B1, and releases the repression of Rht-B1 on GRF4 and BZR1, thereby promoting wheat height, 1000-grain weight and nitrogen use efficiency. ZnF is a positive regulator of brassinosteroid (BR) signaling pathway. BR binding to BRI1 promotes the binding ability of ZnF to BKI1, which directly associates with BRI1 to inhibit BRI1 activity. ZnF promotes BKI1 degradation to activate BRI1 and BR signaling, thereby promoting plant height and 1000-grain weight. Rht-B1 deletion (rht1-bb) activated GA signaling, and resulted in the dramatically increased in plant height, 1000-grain weight and nitrogen use efficiency, whereas ZnF-B deletion (znf-bb) inhibited BR signaling, and led to the reduced plant height and 1000-grain weight. The rht1-bb/znf-bb double mutant did not change the plant height but increased grain yield and nitrogen use efficiency. The “Green Revolution” Rht-B1-ZnF gene module can be used to next generation breeding which aims to crops with high yield and high nitrogen use efficiency. The solid-line arrow indicates activation of the target gene; the dashed-line arrow represents activation of the target gene by an unknown mechanism; the T-shaped solid line indicates inhibition of target gene activity; the T-shaped dashed line represents inhibition of gene activity by an unknown mechanism.

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