Low Isopentenyl Transferase Activity Inhibited Apical Silk Elongation Under Heat and Drought Stress

Abstract

The impact of heat and drought stress on the development of maize reproductive organs is unclear. In this study, heat and drought stress during the ear development stage decreased pollen and silk viability, leading to inhibited apical silk elongation and floret abortion, which further increased the unfertilized silk ratio and reduced the number of kernels. Pollen and silk metabolome analysis revealed that soluble sugar, including sucrose, D-fructose, D-galactose, and D-glucose, changed dramatically in pollen under stress, and cytokinin was the sole phytohormone significantly positively correlated with silk viability under stress. In addition, transcriptome profiling in the crosstalk pathway between zeatin and sugar biosynthesis showed that the lower expression of Zm00001d047253-encoded sucrose synthase enzyme suppressed the transformation of sucrose into D-fructose, possibly resulting in decreased pollen and silk viability under stress. Moreover, low transcript levels of Zm00001d038921 and Zm00001d034584, which encode isopentenyl transferase, in silk restricted cytokinin biosynthesis under stress. Low isopentenyl transferase activity decreased cytokinin content resulting in dwarf silks under stress and exogenous application of cytokinin significantly restored the apical silks under drought stress. These findings provide new insights for breeding maize that is better adapted to climate change to maintain global food security.

Keywords: Abiotic stress, Multi-omics, Cytokinin, Food security