The DlamiR156-DlaSPL60-DlaP5CS1 cascade directly regulates proline synthesis, conferring drought tolerance in Ma bamboo (Dendrocalamus latiflorus Munro).

Abstract

Drought stress disrupts cellular homeostasis and severely limits plant growth. Although proline accumulation is a major adaptive response to water deficit, how drought-responsive regulatory networks control proline biosynthesis in woody grasses remains poorly understood. Here, we combined genetic manipulation, molecular assays, and physiological analyses to investigate the function of the DlamiR156-DlaSPL60 module in Ma bamboo (Dendrocalamus latiflorus Munro). We show that DlamiR156 acts as a negative regulator of drought tolerance by repressing DlaSPL60 via transcript cleavage, whereas drought-induced reduction of DlamiR156 releases this repression; DlaSPL60 directly binds to the DlaP5CS1 promoter and activates its transcription, thereby promoting proline accumulation. Our findings establish a mechanistic link between the conserved miR156-squamosa promoter-binding protein-like regulatory module and proline biosynthesis in bamboo, providing new insights into how post-transcriptional regulation coordinates metabolic reprogramming during drought adaptation in perennial woody grasses.