Barley nuclear cap-binding complex subunits, HvCBP20 and HvCBP80, play distinct roles in drought adaptation at reproductive phase of development

Abstract

Drought remains a major constraint to crop productivity. The nuclear cap-binding complex (CBC), composed of CBP20 and CBP80, regulates pre-mRNA splicing and has been increasingly associated with abscisic acid (ABA) signaling, as suggested by recent studies. Here, we investigated the transcriptomic and physiological impacts of mutations in genes encoding barley nuclear CBC (hvcbp20.ab, hvcbp80.b, and hvcbp20.ab/hvcbp80.b) under drought applied at the booting stage. The mutants exhibited both shared- and mutation-specific adaptations to drought. Transcriptomic profiling revealed that mutation in HvCBP80 significantly reduced transcriptional and splicing activities while inducing the expression of photosynthesis-related genes, resulting in enhanced photosynthetic efficiency under both optimal and drought conditions. Conversely, mutation in HvCBP20 intensified ABA-responsive gene expression and prolonged stress signaling. Physiologically, the hvcbp20.ab mutants displayed increased stomatal conductance despite reduced stomatal density, whereas the hvcbp80.b mutants exhibited decreased conductance under optimal conditions. Despite improved photosynthesis and dehydration avoidance traits, none of the mutations enhanced yield-related parameters under either optimal or drought conditions. Our findings establish that nuclear CBC is a pivotal regulator of drought stress responses and rewatering, capable of reprogramming the transcriptomic landscape to promote enhanced barley resilience.