Abstract
The synthetic enzyme cinnamyl alcohol dehydrogenase (CAD) is involved in responses to various stresses during plant growth. It regulates the monolignol biosynthesis and catalyzes hydroxyl cinnamaldehyde reduction to the corresponding alcohols. Although the CAD gene families have been explored in some species, little known is in Rosaceae. In this study, we identified 149 genes in Pyrus bretschneideri (PbrCAD), Malus domestica (MDPCAD), Prunus mume (PmCAD) and Fragaria vesca (mrnaCAD). They were phylogenetically clustered into six subgroups. All CAD genes contained ADH-N and ADH-zinc-N domains and were distributed on chromosomes unevenly. Dispersed and WGD/segmental duplications accounted the highest number of evolutionary events. Eight collinear gene pairs were identified among the four Rosaceae species, and the highest number was recorded in pear as five pairs. The five PbrCAD gene pairs had undergone purifying selection under Ka/Ks analysis. Furthermore, nine genes were identified based on transcriptomic and stone cell content in pear fruit. In qRT-PCR, the expression patterns of PbrCAD1, PbrCAD20, PbrCAD27, and PbrCAD31 were consistent with variation in stone cell content during pear fruit development. These results will provide valuable information for understanding the relationship between gene expressions and stone cell number in fruit.
Highlights
In plants, the phenolic polymer lignin plays crucial roles in water retention, mechanical support, and protection [1,2,3]
149 Cinnamyl alcohol dehydrogenase (CAD) genes were identified in Rosaceae, including 57 in pear, 34 in Chinese plum, 42 in apple, and 16 in strawberry, named as PbrCAD1-PbrCAD57, MDPCAD1MDPCAD42, PmCAD1-PmCAD34, and mrnaCAD1-mrnaCAD16, respectively (Table 1 and Supplementary Table S1)
A chromosome distribution analysis showed that the CAD genes were unevenly distributed in Rosaceae
Summary
The phenolic polymer lignin plays crucial roles in water retention, mechanical support, and protection [1,2,3]. The content of lignin greatly affects the quality of some fruits, reducing the flavor and quality [4,5]. Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme in the lignin biosynthesis, and the activity of CAD affects the lignin content and monomer composition [8,9]. The CAD gene families and their homologs have been identified in various plants [12,14,15,16,17,18]. No studies have identified the CAD gene family in lignin biosynthesis in pear. We identified the members of the CAD gene family in the pear and three other Rosaceae species. We analyzed the phylogenetic relationships, structures, conserved motifs, synteny, ontology and expression patterns of these genes with the transcriptomic data of PbrCAD gene family
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