Transcriptome analysis unveils a potential novel role of VvAP1 in regulating the developmental fate of primordia in grapevine

Abstract

The grapevine shoot meristem contains undifferentiated primordia known as anlagen, which can develop into either inflorescences or tendrils depending on vine age, growth status, hormone balance, and other factors. Interestingly, a gain-of-function mutation in the DELLA domain of VvDELLA1 in the dwarf mutant grape, Vitis vinifera L. cv. Pixie, virtually disrupts the normal developmental course of anlagen and reroutes tendril-bounded anlagen toward inflorescence development even at the juvenile stage. To understand the underlying mechanism(s), we compared the transcriptome profiles of V. vinifera cv. Pinot Meunier (from which Pixie was derived), Pixie, and three other V. vinifera grape cultivars (Dena, Gina, and Tia) which were derived from crosses involving Pixie and carry the same DELLA mutation. Our findings revealed significant mis-regulation of hundreds of genes, profoundly reshaping both transcriptome landscapes and regulatory pathways in the mutant grapes. Interestingly, VvAP1, a central positive flower regulator in annuals, was unexpectedly co-downregulated with VvTFL1a, a flowering repressor. We also found several other key flower regulators which were either upregulated (e.g., VvFT, VvLFY) or downregulated (e.g., VvSOC1s) in all mutant grapes, although the overall effect was moderate. These findings, along with the previous identification of tendril-specific expression of VvAP1 and inflorescence-specific expression of VvLFY, support that VvAP1 promotes anlagens to develop tendrils, whereas VvLFY favors inflorescences formation. The balance between these factors, particularly the abundance of VvAP1 transcripts, ultimately dictates whether anlagens develop into tendrils or inflorescences.

Keywords

• vitis
• grapevine
• anlagen
• primordia
• vvap1
• inflorescences
• tendrils
• transcriptomes