Mapping and Functional Analysis of a Maize Silkless Mutant sk-A7110

Area of Science:

• Plant Genetics
• Maize Biology
• Reproductive Development

Background:

• Maize silk (stigma) is crucial for reproduction and grain yield.
• Silk development is essential for successful pollination and fertilization in maize (Zea mays).

Purpose of the Study:

• To identify the genetic basis of a spontaneous maize mutant (sk-A7110) that completely lacks silk.
• To investigate the molecular mechanisms underlying silk development defects and their impact on plant reproduction.

Main Methods:

• Isolation and characterization of the sk-A7110 silkless mutant.
• Scanning electron microscopy to observe pistil development.
• Genetic mapping using simple sequence repeat markers.
• Sequence analysis of candidate genes within the mapped interval.
• RNA-sequencing (RNA-seq) to analyze differential gene expression in young ears and tassels.
• Quantification of jasmonic acid (JA) and JA-Isoleucine (JA-Ile) levels.

Main Results:

• The sk-A7110 mutant exhibits complete silk absence, with pistil degeneration during late floret differentiation.
• A single-nucleotide insertion in Zm00001d002970, encoding a UDP-glycosyltransferase, was identified as the causative mutation.
• RNA-seq revealed significant differential gene expression in sk-A7110 ears, with upregulation of genes related to jasmonic acid (JA) synthesis.
• JA and JA-Ile levels were significantly higher in sk-A7110 mutant ears compared to wild type.
• Tassel analysis showed reduced branching in sk-A7110 mutants, linked to downregulation of UB2 and UB3 genes.

Conclusions:

• The identified mutation in Zm00001d002970 is responsible for the silkless phenotype in maize.
• Jasmonic acid signaling pathways are implicated in maize silk development.
• The sk-A7110 mutant provides a valuable tool for studying maize female infertility and for breeding programs aimed at enhancing grain yield.