Comparative characterization and expression analysis revealed cinnamyl alcohol dehydrogenase genes differentially responding to Colletotrichum fructicola in woodland and cultivated strawberries

Abstract

BACKGROUND: Strawberry (Fragaria×ananassa) production is hampered by anthracnose caused by Colletotrichum spp. Cinnamyl alcohol dehydrogenase (CAD) catalyzes lignin biosynthesis to fortify plant cell wall upon various stresses, but their involvement in strawberry resistance is elusive. OBJECTIVE: Current work aims to uncover the involvement of CAD genes in both woodland and cultivated strawberry responses to Colletotrichum spp. METHODS: Genome-wide identification of CAD genes was updated in cultivated strawberry. Comparative molecular characterization integrated with pathogenesis phenotyping after C. fructicola inoculation, were followed by RT-qPCR analysis and RNAseq data retrieval. RESULTS: Cultivated strawberry comprises 32 CAD genes of three classes. Thirteen syntenic relationships were observed between cultivated and woodland strawberry, with high homology in protein coding regions while promoters being greatly diversified. F. vesca ‘Hawaii4’ was least susceptible, followed by octoploid cultivar ‘ShenQi’, and ‘Benihoppe’ the most susceptible to C. fructicola. The class I CAD4 and CAD5, preferentially expressed in leaves and crowns, respectively, were up-regulated in susceptible varieties at 72 h post inoculation (hpi). Of class II, CAD8 was up-regulated in three genotypes at distinct timepoints, while CAD12 was quickly down-regulated in ‘ShenQi’ upon inoculation. CAD1 and CAD2 of class III were down-regulated in ‘ShenQi’ and ‘Hawaii4’ at distinct stages. The strong involvement of CAD genes in strawberry response to Colletotrichum spp. sets a basis for future functional study. CONCLUSION: F. vesca is less susceptible to Colletotrichum spp. than cultivated strawberries but the expression of CAD family in F. vesca and F.×ananassa were differentially provoked in timing and magnitude hinting no correlation with strawberry resistance to this pathogen.