Natural polymorphisms in ZmIRX15A affect water-use efficiency by modulating stomatal density in maize

Area of Science:

• Plant genetics
• Crop science
• Molecular biology

Background:

• Stomatal density (SD) is a crucial trait influencing crop drought resistance and water-use efficiency.
• Identifying the genetic underpinnings of natural SD variation is essential for improving crop resilience.

Purpose of the Study:

• To conduct a genome-wide association study (GWAS) for stomatal density in maize seedlings.
• To identify genetic variants and candidate genes associated with natural variation in SD.
• To elucidate the function of ZmIRX15A in regulating SD and its impact on physiological traits.

Main Methods:

• Genome-wide association study (GWAS) in maize seedlings.
• Identification and characterization of genetic variants, including insertion-deletion (InDel) mutations.
• Analysis of gene function through loss-of-function mutants.
• Transcriptome analysis to assess gene expression changes.
• Biochemical analysis of cell wall composition.

Main Results:

• GWAS identified 18 significant genetic variants linked to seven candidate genes.
• A 3-bp insertion (InDel1089) in Zea mays (Zm) IRX15A showed the strongest association with SD.
• Loss-of-function of ZmIRX15A increased SD, transpiration, and CO2 assimilation efficiency.
• ZmIRX15A dysfunction reduced xylan deposition in secondary cell walls and altered expression of genes related to stomatal development and drought response.

Conclusions:

• ZmIRX15A plays a significant role in regulating stomatal density and xylan biosynthesis in maize.
• The identified genetic variants, particularly in ZmIRX15A, offer potential targets for marker-assisted breeding to enhance drought resistance.
• This study provides valuable genetic insights for improving water-use efficiency in maize through molecular breeding strategies.