The mechanism of newly differentiated leaves of kale turning white in late autumn

Newly differentiated leaves of albino ornamental kale turn white as exposed to low temperatures, producing a distinctive and commercially desirable unique color pattern. Here, we show that this low-temperature-induced albinism is caused by a mutation in the kale F-box gene BoWl. Using yeast two-hybrid, pull-down, co-immunoprecipitation, and luciferase complementation assays, we demonstrate that BoWl interacts with the transcription factor BoARF1 to form a functional complex. Complementary yeast one-hybrid, electrophoretic mobility shift, chromatin immunoprecipitation, and luciferase assays reveal that this complex activates BoGLK1, a regulator of chloroplast development and chlorophyll synthesis. In the albino line, a mutation in BoWl results in abnormal chloroplast structure and disrupts chlorophyll synthesis. We further identify BoCBF1/BoPHL2 as a low-temperature responsive regulatory module that transcriptionally activates BoWl expression. Together, these findings define a molecular pathway linking cold perception to transcriptional regulation associated with leaf whitening in ornamental kale, providing new insight into how low temperature influences genetically controlled leaf color variation.