Scientific Study

Pecan (Carya illinoinensis) is an important nut tree in the world. The high concentration of flavonoid in its kernels makes it an excellent healthy food. However, the molecular basis of flavonoid biosynthesis in pecan remains unclear, which hinders quality breeding in this plant. Therefore, in order to obtain crucial genes involved in flavonoid biosynthesis, the changes in flavonoid profiles and the transcriptomes of four development stages (late water, gel, dough and mature stages) of kernels were analyzed. As a result, the highest levels of total phenolic, condensed tannin and flavan-3-ols were observed at the "late water stage". Catechin was the most abundant flavan-3-ol at different development stages. In total, 64,773 unigenes were obtained, and 46,924 (72.44%) unigenes were annotated. After differentially expressed gene (DEG) analysis, 12,750 unique DEGs were identified. Flavonoid-related DEGs of 36 structural genes and 8 MYBs were obtained. The structural gene set contained 3 PALs, 3 CHSs, 2 CHIs, an F3H, 2 F3'Hs, 2 F3'5'Hs, 1 DFR, 1 ANS, 2 LARs and 2 ANRs. The expression patterns of most of the structural genes were consistent with the changes in flavonoid profiles during kernel development. We believe that this RNA-Seq dataset will provide valuable resources for unraveling the molecular mechanism of flavonoid metabolism in pecan and will significantly promote the genetic study and quality breeding in this plant.