A key structural gene, AaLDOX, is involved in anthocyanin biosynthesis in all red-fleshed kiwifruit (Actinidia arguta) based on transcriptome analysis

Study on kiwifruit (Actinidia chinensis and A. deliciosa) color mainly concentrated in green and yellow-fleshed cultivars, less about molecular mechanism of red-fleshed trait formation, rarely in all red-fleshed fruit. Using 'Tianyuanhong' and 'Yongfengyihao' ('TY', a kind of all red-fleshed cultivar, from Actinidia arguta; 'YF', a kind of all green-fleshed cultivar, also from Actinidia arguta) as experimental material, we performed RNA-seq to obtain 202,742 unigenes with an average length of 603 bp and N50 of 873 bp via transcriptome data analysis. Of these unigenes, 72,508 (35.76%) were annotated and 997 were assigned to secondary metabolic pathways, of which 104 unigenes were involved in flavonoid and anthocyanin biosynthesis. According to the parameter log2fold-change and p-adjusted, 12 differentially expressed structural genes were selected for performing expression profiles and cluster analysis. Physiological traits including color ration, hue angle, and anthocyanin content were also investigated. From the results, we concluded AaLDOX (genes encoding leucoanthocyanidin dioxygenase) maybe the key gene controlling anthocyanin biosynthesis in flesh of 'TY' kiwifruit, which promoted accumulation of anthocyanin, finally leading to the red flesh coloration.