Transcriptomics Reveals Cold Tolerance Maize Lines Involved in the Phenylpropanoid and Flavonoid Pathways

Area of Science:

• Plant Science
• Agronomy
• Molecular Biology

Background:

• Low spring temperatures negatively impact maize germination and crop yields.
• Understanding the genetic and molecular basis of maize cold tolerance is vital for agricultural productivity.

Purpose of the Study:

• To investigate the molecular mechanisms underlying cold tolerance in maize during germination.
• To compare the responses of cold-tolerant and cold-sensitive maize inbred lines to chilling stress.

Main Methods:

• Phenotypic analysis of germination and coleoptile elongation under control and chilling conditions.
• Biochemical assays for antioxidant enzyme activity (SOD, POD) and malondialdehyde content.
• Transcriptome profiling (RNA-seq) to identify differentially expressed genes.
• Quantitative real-time PCR (qRT-PCR) for gene expression validation.

Main Results:

• Cold-tolerant maize lines (AM, CM) maintained high germination rates and coleoptile elongation under chilling (6 °C), unlike the sensitive line (BM).
• Tolerant lines exhibited lower malondialdehyde levels and higher superoxide dismutase (SOD) and peroxidase (POD) activities, indicating superior antioxidant capacity.
• Transcriptome analysis revealed significant upregulation of phenylpropanoid and flavonoid biosynthesis pathways in cold-tolerant lines.
• The class III peroxidase gene ZmPER5, along with lignin and flavonoid biosynthesis genes (ZmHCT4, ZmCYP75), showed genotype-specific expression patterns linked to cold tolerance.

Conclusions:

• Maize cold tolerance at germination is a complex trait involving enhanced antioxidant systems and specific metabolic pathways.
• Activation of phenylpropanoid-derived lignin biosynthesis and flavonoid accumulation contribute to cold resilience.
• ZmPER5 and other identified genes are promising targets for breeding cold-tolerant maize varieties.