Ferritin-Mediated Iron Homeostasis and Bacterial Shifts Are Associated With Drought Adaptation in Sorghum.

Abstract

Drought stress significantly impairs growth and microbial interactions in sorghum. This study explores the transcriptional and microbial shifts in sorghum under drought, revealing key adaptations to water deficit. LC-MS (liquid chromatography-mass spectrometry) analyses revealed that drought stress induced abscisic acid while significantly reducing jasmonic acid levels in sorghum roots, likely due to resource conservation strategies during drought. Transcriptional reprogramming highlighted the upregulation of genes in the roots involved in mineral homeostasis (Ferritin 1, Iron dehydrogenase, Nitrate transporter 1), hormone signaling (Ethylene-insensitive protein 3, Gibberellin 2-oxidase), and osmotic regulation (Aquaporin, Dehydrin), underlining key adaptive responses to maintain nutrient uptake, redox status, and cellular turgor. In Fe-supplemented plants, increased Fe in roots correlated with increased Ferritin 1 expression, improved plant health, and reduced Fenton reaction rate and H₂O₂ levels. This suggests that ferritin helps mitigate drought-induced oxidative stress in sorghum. Drought reduced root-associated bacterial diversity and richness while enriching drought tolerance-associated genera, such as Burkholderia, Caballeronia, and Paraburkholderia, known for promoting plant growth through auxin production, phosphate solubilization, and siderophore-mediated iron acquisition. In contrast, fungal diversity and richness remained unchanged, dominated by Talaromyces, which showed a statistically non-significant increase under drought. Random forest models could not identify functional predictors for fungi but revealed a shift in bacterial functional groups under drought, with enrichment in phototrophy, methylotrophy, and nitrate reduction, traits emphasizing microbial roles in nutrient cycling and drought adaptation of sorghum. This study provides insights into the role of ferritin and potential bacterial bioinoculants that could enhance sorghum resilience to drought.