Transcriptome and weighted gene co-expression network analysis reveal key genes involved in the proanthocyanidin biosynthesis in Cerasus humilis

Abstract

Proanthocyanidins (PAs), contributing greatly to the antioxidant activity, are among the most abundant flavonoid components in Cerasus humilis fruits. In this study, contents of six different PA components and total PAs in fruits of two C. humilis varieties (‘Jinou1’ and ‘DS-1′) were determined at four different ripening stages. Results showed that, five PA components and the total PAs contents of ‘Jinou1’ were notedly higher than that of ‘DS-1′ except proanthocyanidins A1. All PA components showed a general decreasing trend during ripening, and dropped to their lowest levels at the fully ripe stage. In ripe C. humilis fruits, the major PA was catechin, the content of which undergoes considerable changes during fruit ripening. The key genes involved in PA biosynthesis were explored based on the transcriptome profiles, and their co-expression networks were constructed. Transcriptomic analysis identified 19 PA biosynthesis-related structural genes as differentially expressed genes (DEGs). The highly expressed MSTRG.938 (LAR, leucoanthocyanidin reductase), MSTRG.4502 (ANR, anthocyanidin reductase), and MSTRG.4956 (PAL, phenylalanine ammonia lyase) genes may play key roles in regulating PA accumulation. Moreover, through weighted gene co-expression network analysis (WGCNA), we constructed a gene regulatory network of two modules involving 15 PA biosynthesis-related DEGs, and the expression changes in 10 of them were validated using quantitative real-time PCR. These results indicated that they are key contributors to the PA biosynthesis in C. humilis fruits. Our study will aid in elucidating the molecular mechanisms underlying PAs accumulation in C. humilis fruits.