Integrating physiological, metabolome and transcriptome revealed the response of maize seeds to combined cold and high soil moisture stresses.

Abstract

Combined cold and high moisture stress (CHS) is a prevalent abiotic stress during maize sowing in northeast China, severely affecting the growth of seedlings and seed germination. However, the mechanism underlying seed growth responses to CHS remains unclear. We used Jidan441 (JD441, CHS-resistant) and Jidan558 (JD558, CHS-sensitive) as experimental materials. Treatments of 5-day cold (4°C, CS), high moisture (25%, gravimetric water content, HH), and CHS were initiated at sowing, followed by a return to normal growth conditions (20°C during light/ 15°C during dark, 15%) at 7 days after sowing (DAS). CS, HH, and CHS decreased seed root length and surface area. The reduction in root length and surface area in JD441 due to CHS was less severe than in JD558. We found that the difference between CHS and control in JD441was less than that in JD558 at transcriptional and metabolic levels at 7 DAS. After CHS removal, JD441 exhibited a greater increase in α-amylase activity and antioxidant content than JD558, which facilitated starch decomposition and the rapid removal of O₂ ^- and H₂O₂ in seeds. The rapid recovery of soluble sugar and soluble protein in JD441 helped maintain osmotic balance. Amino acids and genes related to amino acid metabolism were upregulated in response to combined stress in JD441, whereas they were downregulated in JD558. In conclusion, the stress tolerance of JD441 was attributed to its efficient recovery ability from CHS. This study provides a scientific foundation for exploring seed stress tolerance pathways and developing cold and high-moisture-tolerant hybrids.