Locally restricted glucose availability in the embryonic hypocotyl determines seed germination under ABA treatment

Abstract

SummaryAbiotic stresses directly affect seed germination, plant growth, and reproduction. Seed germination is a complex and energy-demanding process, involving diverse physical, metabolic and cellular events, and is controlled by intrinsic and environmental cues. Abiotic stresses involving abscisic acid (ABA) inhibit seed germination by suppressing physiological processes essential for completion of germination. It remains unclear whether the component tissues of an embryo respond to stress, and are suppressed differentially.Here we used a genetically engineered FRET sensor to show that ABA significantly affected the spatiotemporal distribution of glucose (Glc) in lower hypocotyl region. Transcriptome analysis and 14C-Glc uptake assay suggested that Glc limitation in the embryonic hypocotyl was largely due to suppressed sugar partitioning along with enhanced sugar metabolism. The loss-of-function mutants of ABA-induced sucrose-phosphate synthase (SPS) genes accumulated more Glc, leading to ABA insensitivity during germination. In addition, we identified molecular signatures that Glc antagonizes ABA by globally counteracting the ABA influence on gene expression, including expansin (EXP) family genes that are inhibited by ABA.This study presents a new perspective on the interaction between ABA and Glc in response to external stimuli, which restricts Glc availability and thereby controls the transition from seed to seedling.