Flavonoid content and radical scavenging activity in fruits of Chinese dwarf cherry(Cerasus humilis) genotypes

The Chinese dwarf cherry（Cerasus humilis（Bge.） Sok.） is a small shrub with edible fruits. It is native to northern and western China. This species was included as a medicinal plant in the ‘‘Chinese Pharmacopeia’’ and has emerged as an economically important crop for fresh fruit consumption, processing into juice and wine and nutraceutical products as well. To gain a better understanding of flavonoid biosynthesis and help develop value added products and better cultivars with greater health benefits, we analyzed total flavonoid content（TFC）, composition, and radical scavenging activities in fruit extracts of 16 Chinese dwarf cherry genotypes. Fruit peel TFC ranged from 33.5 to72.8 mg/g REáFW（RE： rutin equivalent, FW： fresh weight）while fruit flesh TFC ranged from 4.3 to 16.9 mg/g REáFW.An HPLC analysis revealed that fruit extracts contained 14 flavonoids with considerable variation in their profiles across genotypes. The most abundant flavonoids in most genotypes were proanthocyanidin B1（PA-B1）, proanthocyanidin B2（PA-B2）, phloretin 20-O-glucoside（PG）, and phloretin 20,40-O-diglucoside（PDG）. Principal component analysis showed that PG, PA-B1, and PA-B2 had large,positive factor loading values in the first principal component for each genotype. Increased scavenging activity of2,2-diphenyl-1-picrylhydrazyl（DPPH） radicals was apparent in genotypes ‘Nongda 4’, ‘Nongda 3’, ‘Nongda 6’,‘Wenfenli’, and ’10-32’, suggesting promising applications in the production of nutraceutical products. In summary, our results will aid in breeding, fruit processing, and developing medicinal uses of the Chinese dwarf cherry.

Comprehensive transcriptomic analysis of developing seed in Cerasus humilis for lipid related gene discovery

Cerasus humilis is a woody shrub with increasing economic importance. Due to its high oil content in seed with desired fatty acid(FA) composition, C. humilis has been considered as a potential woody oilseed crop in China. However, FAs accumulation and related molecular mechanisms of FA biosynthesis in C. humilis seed have not been elucidated well. In this study, oil contents and FA compositions of developing C. humilis seed were analyzed. The total oil content in mature seed reached 48.7% while unsaturated FA concentration reached a high level of 96.2%. Three c DNA libraries of C. humilis developing seed were constructed at the beginning and 2 fast oil-accumulation stages, followed by Illumina sequencing with the platform of HiSeq^TM 2000. Differentially expressed unigenes(DEGs) were identified during the respective seed development stages to investigate transcription dynamics. Among DEGs, 82 unigenes were identified as being closely involved in de novo FA and triacylglycerol(TAG) biosynthesis. Surprisingly, among DEGs involved in TAG biosynthesis, expression of unigenes encoding GPATs(glycerol-3-phosphate acyltransferase) were relatively low and unigenes encoding LPAATs(lysophosphatidic acid acyltransferase) were highly expressed, suggesting that LPAAT contributed more in storage lipids metabolism in C. humilis seed. Genes encoding DGAT2(diacylgycerol acyltransferase2) were the most highly expressed while expression of DGAT1 was very low, suggesting DGAT2 was the dominant DGAT which catalyzed TAG biosynthesis. To verify these results,10 unigenes were selected and their expression patterns were analyzed by quantitative RTPCR. These data provided comprehensive information for understanding the molecular mechanism of FA and TAG biosynthesis in C. humilis seed.