Brassinolide Alleviates Maize Silk Growth Under Water Deficit by Reprogramming Sugar Metabolism and Enhancing...

Area of Science:

• Plant Physiology
• Agricultural Science
• Molecular Biology

Background:

• Drought stress severely impacts maize reproduction by arresting silk elongation, leading to anthesis-silking interval increases and kernel loss.
• Exogenous brassinosteroids (BR) are known to enhance plant drought tolerance, but their specific effects on maize silk growth under water deficit were unclear.

Purpose of the Study:

• To investigate the impact of foliar brassinosteroid (BR) application on maize silk elongation under drought stress.
• To elucidate the physiological and molecular mechanisms underlying BR-mediated protection of silk growth against water deficit.

Main Methods:

• Maize plants were subjected to drought stress, followed by foliar application of varying BR concentrations (0, 0.1, 0.5, 1 mg mL⁻¹).
• Silk length, antioxidant enzyme activities (POD, SOD, CAT), proline content, oxidative damage markers (O₂⁻, H₂O₂, MDA), and key enzyme activities (SPS, SS-I, VIN) were measured.
• Genome-wide RNA sequencing (RNA-seq) was performed to identify differentially expressed genes and enriched pathways.

Main Results:

• BR at 0.1 and 0.5 mg mL⁻¹ partially restored silk elongation under drought, with 0.5 mg mL⁻¹ increasing silk length significantly.
• BR treatment elevated antioxidant capacity and proline levels, reducing oxidative damage, and reprogrammed sugar metabolism by increasing hexose production.
• RNA-seq revealed significant changes in gene expression, particularly in starch/sucrose metabolism, glycolysis, and phenylpropanoid biosynthesis pathways, with key genes like INV and HK upregulated.

Conclusions:

• Brassinosteroids (BR) effectively mitigate drought-induced silk growth arrest in maize by enhancing antioxidant defense and osmotic adjustment.
• BR promotes silk growth under stress through metabolic reprogramming, shifting carbon partitioning towards hexoses to support energy demands.
• BR-mediated stress adaptation involves a complex network of physiological and molecular responses, offering mechanistic insights into reproductive stage drought tolerance in maize.