Functional Characterization of Rose ABC Transporters Identifies RcABCG5/50/59 as Candidate Genes Associated with Botrytis cinerea Resistance

Abstract

Gray mold caused by Botrytis cinerea severely limits the postharvest quality of rose, but the contribution of ATP-binding cassette (ABC) transporters to rose defense remains unclear. Here, we identified 185 RcABC genes in the Rosa chinensis genome and classified them into eight subfamilies, with RcABCG as the largest subfamily. DESeq2-based RNA-seq analysis identified 13 significantly upregulated RcABC genes in response to B. cinerea infection at 48 hpi, nine of which belonged to the RcABCG subfamily. At 48 hpi, the log2 fold changes of these induced genes ranged from 1.34 to 7.98, and RcABCG5, RcABCG50, RcABCG59, and RcABCG60 were selected for functional analysis. Further phylogenetic, gene-structure, and promoter analyses showed that several full-size RcABCG members were closely related to previously reported defense-associated ABCG transporters and harbored predicted GA-, MeJA-, and ABA-responsive cis-elements. Virus-induced gene silencing reduced the relative transcript levels of RcABCG5, RcABCG50, RcABCG59, and RcABCG60 to 22.8%, 17.9%, 35.2%, and 27.5% of the TRV-GFP control, respectively. Mean lesion area increased from 39.27 mm2 in TRV-GFP discs to 44.96, 46.95, and 43.23 mm2 in RcABCG5-, RcABCG50-, and RcABCG59-silenced discs, respectively, whereas no significant lesion increase was observed in RcABCG60-silenced discs. Together, these results establish a genome-wide framework for defense-related ABC transporters in rose and identify RcABCG5/50/59 as candidate genes associated with gray mold resistance under VIGS conditions.