DcGATA22 serves as a transcription factor positively coordinating chlorophyll and carotenoid accumulation in carrot

Overexpression of DcGATA22 in carrot calli enhanced carotenoid accumulation and elevated the carotenoid ester levels. It increased chlorophyll and carotenoid contents in leaves and exhibited potential photoresponsivity. Pigments such as chlorophylls and carotenoids give plants diverse color and play important roles in biological processes. Carrot (Daucus carota) presents colorful germplasm resources due to variation in carotenoid composition. Cytokinin-responsive GATA factor1/GNC-like (GNL) is a member of the B-GATA subfamily that affects chlorophyll biosynthesis. However, its role in carotenoid metabolism remains unclear, and little is known about its function in carrot. This study reveals the effects of the AtGNL homolog DcGATA22 on chlorophyll and carotenoid synthesis in carrot. Overexpression of DcGATA22 enhanced carotenoid content in orange carrot calli, especially β-carotene, and elevated the levels of some carotenoid esters, such as violaxanthin dimyristate, violaxanthin palmitate, and antheraxanthin. In wild calli, violaxanthin palmitate was almost undetectable, whereas its concentration in transgenic calli amounted to 7.1 µg/g FW. The expression level of DcPSY1, which encodes a rate-limiting enzyme in the carotenoid biosynthesis pathway, was significantly increased in the transgenic calli. Overexpressing DcGATA22 promoted chlorophyll and carotenoid accumulation in carrot leaves. In the transgenic leaves, the expression levels of genes involved in chlorophyll and carotenoid synthesis pathways such as DcHEMA, DcCHLH, DcPSY1, and DcPDS were significantly increased. In addition, DcGATA22 was down-regulated in shaded leaves, suggesting it may be light-induced. These results provide preliminary insight into the positive effects of DcGATA22 on carotenoids and chlorophylls in carrot.