Coordinated Chlorophyll Degradation and Flavonoid Accumulation Orchestrate Leaf Variegation of Sasaella kogasensis...

Leaf variegation represents a striking natural phenomenon where distinct pigmentation patterns develop within individual leaves, yet the underlying molecular mechanisms remain poorly understood. Here, we investigated yellow stripe formation in the ornamental bamboo Sasaella kogasensis 'Aureostriatus' using integrated physiological, cellular, and multi-omics approaches. Yellow stripe development followed a 240-day progression of spatially restricted senescence, with yellow zones showing accelerated chloroplast degradation and reduced chlorophyll content. Ultrastructural analysis revealed progressive chloroplast shrinkage, thylakoid swelling, and osmiophilic granule accumulation in yellow zones. Multi-omics profiling identified flavonoids as predominant differentially accumulated metabolites (16.79% of 1227 detected), with 177-fold upregulation of chrysoeriol O-malonylhexoside, alongside 6951 differentially expressed genes showing coordinated downregulation of photosynthesis and upregulation of chlorophyll degradation pathways. We identified three key regulatory genes (SkSGR, SkNAC021, and SkNAC29) whose roles were validated through transgenic Arabidopsis experiments demonstrating premature senescence and chlorophyll degradation. Hormone profiling revealed zone-specific accumulation of abscisic acid, salicylic acid, and jasmonic acid precursors. Our findings demonstrate that yellow stripe formation involves coordinated regulation of chloroplast degradation, flavonoid biosynthesis, and senescence-associated networks, providing molecular insights into natural leaf variegation patterns.