VviERF6Ls: an expanded clade in Vitis responds transcriptionally to abiotic and biotic stresses and berry development.

BACKGROUND

VviERF6Ls are an uncharacterized gene clade in Vitis with only distant Arabidopsis orthologs. Preliminary data indicated these transcription factors may play a role in berry development and extreme abiotic stress responses. To better understand this highly duplicated, conserved clade, additional members of the clade were identified in four Vitis genotypes. A meta-data analysis was performed on publicly available microarray and RNA-Seq data (confirmed and expanded with RT-qPCR), and Vitis VviERF6L1 overexpression lines were established and characterized with phenotyping and RNA-Seq.

RESULTS

A total of 18 PN40024 VviERF6Ls were identified; additional VviERF6Ls were identified in Cabernet Sauvignon, Chardonnay, and Carménère. The amino acid sequences of VviERF6Ls were found to be highly conserved. VviERF6L transcripts were detected in numerous plant organs and were differentially expressed in response to numerous abiotic stresses including water deficit, salinity, and cold as well as biotic stresses such as red blotch virus, N. parvum, and E. necator. VviERF6Ls were differentially expressed across stages of berry development, peaking in the pre-veraison/veraison stage and retaining conserved expression patterns across different vineyards, years, and Vitis cultivars. Co-expression network analysis identified a scarecrow-like transcription factor and a calmodulin-like gene with highly similar expression profiles to the VviERF6L clade. Overexpression of VviERF6L1 in a Seyval Blanc background did not result in detectable morphological phenotypes. Genes differentially expressed in response to VviERF6L1 overexpression were associated with abiotic and biotic stress responses.

CONCLUSIONS

VviERF6Ls represent a large and distinct clade of ERF transcription factors in grapevine. The high conservation of protein sequence between these 18 transcription factors may indicate these genes originate from a duplication event in Vitis. Despite high sequence similarity and similar expression patterns, VviERF6Ls demonstrate unique levels of expression supported by similar but heterogeneous promoter sequences. VviERF6L gene expression differed between Vitis species, cultivars and organs including roots, leaves and berries. These genes respond to berry development and abiotic and biotic stresses. VviERF6L1 overexpression in Vitis vinifera results in differential expression of genes related to phytohormone and immune system signaling. Further investigation of this interesting gene family is warranted.