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Rht4 is characterized as a GA‐responsive dwarf gene in bread wheat (Triticum aestivum L.). The responsiveness of Rht4 to exogenous GA3 was characterized in seedlings, but the effects of exogenous GA3 on the important morphological and agronomic traits such as plant height, grain‐filling rate, and yield components are unclear. In this study, the Rht4 responsiveness of exogenous GA3 on these traits was evaluated using the homozygous F4:5 and F5:6 lines derived from a cross between Jinmai47 and Burt ert937 (Rht4 donor). After exogenous GA3 application, the plant height of the dwarf lines was, on average, increased by 17.54%, about 7.92% more than that of the tall lines. Compared with the tall lines, application of exogenous GA3 significantly increased the kernel weight, maximum grain‐filling rate (Gmax), average grain‐filling rate (Gave) and kernel weight increment achieving Gmax (Wmax) in both superior and inferior grains, while the day on which the maximum grain‐filling rate was reached (Tmax) in Rht4 dwarf lines was significantly earlier in the two generations. What is more, the grain number spike−1, grain yield plant−1, and 1000‐kernel weight (TKW) of the dwarf lines notably increased after exogenous GA3‐treatment, while there was no significant change in the tall lines except for TKW. The quality traits of the dwarf lines with GA3‐treatment were greatly improved. Taken together, these results suggested that the application of GA3 could improve the grain‐filling process of Rht4 and compensate for some negative influences, which may provide a reference for its application in wheat breeding and promote the characterization of its regulatory mechanisms. [ABSTRACT FROM AUTHOR]

Rht14, was considered as a GA‐responsive dwarf gene in durum wheat (Triticum durum L.). The object of this paper is to understand the responsiveness of Rht14 after applying exogenous GA3 on important morphological and agronomic traits, and its potential application in wheat breeding. In this study, the F2:3 lines, F3:4 lines and F4:5 lines derived from the reciprocal crosses between the Castelporziano (CP), the donor of Rht14, and tall cultivar Langdon (L) were used to evaluate the effects of Rht14 with exogenous GA3 application on crucial traits. After application of GA3, the plant height of the dwarf lines was more significantly increased by an average of 51.21% and 52.27% than that of the tall lines by 14.70% and 15.16% of the two populations, respectively, while their diameter and thickness of internodes were remarkably reduced, and their flag leaf area, SPAD value and net photosynthetic rate were markedly decreased, compared with the controls. After application of GA3, the spikelet number spike−1, grain number spike−1, and 1000‐kernel weight of the dwarf lines notably increased, while no significant differences were observed on the seed length, width and thickness. Exogenous GA3 significantly increased the coleoptile length, whereas notably reduced the max root length and total root length of the dwarf lines. Significant increases of crude protein, wet gluten, sedimentation value, stability time and development time were observed in the dwarf lines treated with GA3. This study indicated the dwarf gene Rht14 was a GA‐deficient gene and application GA3 could rescue some negative effects by Rht14. [ABSTRACT FROM AUTHOR]

Compared to C 3 species, C 4 plants showed higher photosynthetic capacity as well as water and nitrogen use efficiency due to the presence of the C 4 photosynthetic pathway. Previous studies have shown that all genes required for the C 4 photosynthetic pathway exist in the genomes of C 3 species and are expressed. In this study, the genes encoding six key C 4 photosynthetic pathway enzymes (β-CA, PEPC, ME, MDH, RbcS, and PPDK) in the genomes of five important gramineous crops (C 4 : maize, foxtail millet, and sorghum; C 3 : rice and wheat) were systematically identified and compared. Based on sequence characteristics and evolutionary relationships, their C 4 functional gene copies were distinguished from non-photosynthetic functional gene copies. Furthermore, multiple sequence alignment revealed important sites affecting the activities of PEPC and RbcS between the C 3 and C 4 species. Comparisons of expression characteristics confirmed that the expression patterns of non-photosynthetic gene copies were relatively conserved among species, while C 4 gene copies in C 4 species acquired new tissue expression patterns during evolution. Additionally, multiple sequence features that may affect C 4 gene expression and subcellular localization were found in the coding and promoter regions. Our work emphasized the diversity of the evolution of different genes in the C 4 photosynthetic pathway and confirmed that the specific high expression in the leaf and appropriate intracellular distribution were the keys to the evolution of C 4 photosynthesis. The results of this study will help determine the evolutionary mechanism of the C 4 photosynthetic pathway in Gramineae and provide references for the transformation of C 4 photosynthetic pathways in wheat, rice, and other major C 3 cereal crops., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Chen, Yang, Zhao, Lu, Lu, Cui, Parry and Hu.)