A truncated RNase H-like protein underlining Rht8 to regulate the ‘Green Revolution’ trait in wheat

Authors: CHAI, LINGLING - China Agricultural University; XIN, MINGMING - China Agricultural University; DONG, CHAOQUN - China Agricultural University; CHEN, ZHAOYUN - China Agricultural University; ZHAI, HUIJIE - China Agricultural University; CHENG, XUEJIAO - China Agricultural University; WANG, NAIJIAO - China Agricultural University; GENG, JIA - China Agricultural University; BIAN, ROULIN - Kansas State University; Bai, Guihua; YAO, YINGYIN - China Agricultural University; GUO, WEILONG - China Agricultural University; HU, ZHAORONG - China Agricultural University; PENG, HUIRU - China Agricultural University; SUN, QIXIN - China Agricultural University; SU, ZHENQI - China Agricultural University; LIU, JIE - China Agricultural University; NI, ZHONGFU - China Agricultural University

Submitted to: Molecular Plant
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2022
Publication Date: 1/18/2022
Citation: Chai, L., Xin, M., Dong, C., Chen, Z., Zhai, H., Cheng, X., Wang, N., Geng, J., Bian, R., Bai, G., Yao, Y., Guo, W., Hu, Z., Peng, H., Sun, Q., Su, Z., Liu, J., Ni, Z. 2022. A truncated RNase H-like protein underlining Rht8 to regulate the ‘Green Revolution’ trait in wheat. Molecular Plant. https://doi.org/10.1016/j.molp.2022.01.013.
DOI: https://doi.org/10.1016/j.molp.2022.01.013

Interpretive Summary: Introduction of Reduced Height (Rht) genes (Rht-B1b and Rht-D1b) into modern wheat cultivars has resulted in the development of high-yielding ‘Green Revolution’ semi-dwarf wheat varieties. The two Rht genes are gibberellin-insensitive and reduce both plant height and coleoptile length. Reduced coleoptile length negatively affects seedling establishment in dryland regions. Rht8, however, is gibberellin-sensitive and only reduces plant height, but not coleoptile length. We cloned Rht8 and showed it is a putative Ribonuclease H-domain containing nuclear protein. Rht8 confers semi-dwarfism by increasing ethylene response and reducing gibberellin levels. Rht8 is highly conserved in monocot and dicot plants. Therefore, plant height can be manipulated in many crops by gene editing Rht8 to improve crop yield.

Technical Abstract: Introduction of Reduced height (Rht) genes into modern wheat cultivars has resulted in ‘Green Revolution’ that skyrocketed wheat grain yields worldwide since 1960s. These ‘Green Revolution’ cultivars show shorter plant height, but higher lodging-resistance and harvest index under modern high-input farming system. The gibberellin (GA)-insensitive Rht genes, Rht-B1b and Rht-D1b, are the major contributors to the green revolution, which encode truncated DELLA proteins to represses wheat plant growth by reducing plant response to GA. However, Rht-B1b/D1b also reduce coleoptile, which is undesired in dryland regions where deep planting is essential for seedling establishment. Rht8 is GA-sensitive Rht gene with no deleterious effects on seedling vigor and grain traits, thus is a preferred source of semi-dwarf genes for wheat breeding. However, it’s identity remains unknown, which hampers its deployment in wheat. Here, we cloned Rht8 as a putative Ribonuclease H-domain containing nuclear protein (RNHC-D1) using map-based cloning. RNHC-D1 acts as a negative regulator of plant height to confer Rht8 semi-dwarfism by increasing ethylene response and reducing bioactive GA levels. Sequence analyses of RNHC1 orthologs from different species reveal it as a conserved gene in cereal crops. Functional analysis of RNHC1 orthologs from maize and Arabidopsis using gene editing confirmed it as plant height reducing genes in both dicot and monocot species. Conservative function of RNHC1 across species suggests that plant height in diverse crop species can be manipulated by genetically engineering of RNHC1 to improve crop yield.