image: Natural variations in ZmCCT2 regulate maize mesocotyl elongation and higher altitude adaptation
Credit: ©Science China Press
The mesocotyl, a crucial organ for cereal crops, plays a key role in seedling establishment by pushing buds out of the soil during germination. In arid/semiarid or cold regions, mesocotyl length is a target for selection and improvement in breeding of maize varieties tolerant to deep-sowing, a strategy that enables maize seeds to absorb water in deeper soil layers and germinate normally. Due to the genetic diversity of maize, some plants have developed long mesocotyls capable of deep-sowing, while others are unable to do that due to short mesocotyls. Large efforts have been made to map a number of quantitative trait loci (QTLs) regulating maize mesocotyl length with multiple linkage populations, but the causal genes and molecular mechanisms remain poorly understood due to the fact that no QTL has been cloned to date, the genetic mechanisms that control maize mesocotyl length remain largely unknown.
In this study, researchers have made a groundbreaking discovery in maize genetics, uncovering the pivotal role of natural variations in the ZmCCT2 gene in regulating mesocotyl elongation and adaptation to high altitudes.
Through a comprehensive investigation involving a diverse panel of 364 maize inbred lines, the team identified significant associations between specific genetic variations and mesocotyl lengths. Notably, the ZmCCT2 gene emerged as a central player, with overexpression of ZmCCT2 leading to enhanced mesocotyl development, while its knockout resulted in shorter mesocotyls. These findings underscore the essential function of ZmCCT2 in promoting cell elongation and mesocotyl growth in maize seedlings.
Furthermore, the study revealed a novel molecular pathway involving ZmCCT2, ZPUM5, ZmEXPs, and ZmPIFs, shedding light on the intricate mechanisms through which maize seedlings orchestrate mesocotyl elongation. The researchers also identified distinct haplotypes of ZmCCT2 associated with either long or short mesocotyls, with the long mesocotyl haplotype ZmCCT2TypeA favoring adaptation to high altitudes.
Professor Mingqiu Dai remarked, "The study not only deepens our comprehension of the genetic regulation of maize mesocotyl elongation but also furnishes valuable insights and molecular markers for breeding deep-sowing-tolerant maize varieties."
In essence, this research illuminates the critical function of ZmCCT2 in governing maize mesocotyl elongation and adaptation to higher altitudes, opening up innovative pathways for enhancing maize cultivation in diverse agricultural settings. These findings not only enrich the genetic repertoire of maize but also hold promise for the development of maize varieties resilient to deep sowing, emphasizing the potential impact of this study on agricultural production and food security.
This research was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, and the Natural Science Foundation of Hubei Province.