# Transcriptome and VcCADs gene family analyses reveal mechanisms of blight resistance in rabbiteye blueberry

## TL;DR

This study identifies genes involved in lignin synthesis that help rabbiteye blueberries resist branch blight caused by a fungal pathogen.

## Contribution

The study characterizes the CAD gene family and links specific gene expression to enhanced blight resistance in blueberries.

## Key findings

- Resistant blueberry cultivar 'TF' showed higher lignin content and enzyme activity compared to susceptible 'DF'.
- RNA-seq identified 136 and 121 lignin-related differentially expressed genes in 'TF' and 'DF', respectively.
- VcCAD8 and VcCAD62 genes were significantly upregulated in resistant blueberries after pathogen inoculation.

## Abstract

Blueberry branch blight is a severe plant disease primarily caused by Neofusicoccum parvum.

In this study, one-year-old branches of two rabbiteye blueberries (Vaccinium virgatum): resistant Tifblue ('TF') and susceptible Climax ('DF') were selected as experimental materials, the physiological parameters of two cultivars pre- and post- N. parvum inoculation. Transcriptomic analysis and comprehensive gene family characterization were conducted to examine the differential gene expression.

The results indicated that 'TF' exhibited higher lignin content and activity levels of peroxidase enzymes (POD), phenylalanine ammonia-lyase (PAL), and cinnamyl alcohol dehydrogenase (CAD) compared to 'DF'. RNA-sequence analysis revealed that at 24 hours post-inoculation, there were 136 and 121 differentially expressed genes related to lignin synthesis in 'TF' and 'DF', respectively. The analysis of these DEGs revealed that numerous of key enzyme genes in lignin synthesis pathways, including PAL, 4CL, CCR, CAD, HCT, COMT and POD were annotated. Additionally, we characterized the CAD gene family, identifying 93 CAD coding genes at the blueberry genome level, which were classified into four subgroups. Most CAD gene promoters contained response elements associated with plant stress resistance pathways. QRT- PCR experiments demonstrated that the expression levels of VcCAD8 and VcCAD62 genes were significantly upregulated at 24 hours post-inoculation.

These findings suggest that VcCADs enhance lignin synthesis, improve the resistance of blueberries to shoot blight, and provide novel insights into the defense mechanisms of blueberries against N. parvum.