Abstract

   Fruit development in Lycium ruthenicum Murr. involves a succession of
   physiological and biochemical changes reflecting the transcriptional
   modulation of thousands of genes. Although recent studies have
   investigated the dynamic transcriptomic responses during fruit ripening
   in L. ruthenicum, most have been limited in scope, and thus systematic
   data representing the structural genes and transcription factors
   involved in anthocyanin biosynthesis are lacking. In this study, the
   transcriptomes of three ripening stages associated with anthocyanin
   accumulation, including S1 (green ripeness stage), S2 (skin color
   change) and S3 (complete ripeness stage) in L. ruthenicum were
   investigated using Illumina sequencing. Of a total of 43,573 assembled
   unigenes, 12,734 were differentially expressed during fruit ripening in
   L. ruthenicum. Twenty-five significantly differentially expressed
   structural genes (including PAL, C4H, 4CL, CHS, CHI, F3H, F3’H, F3’5’H,
   DFR, ANS and UFGT) were identified that might be associated with
   anthocyanin biosynthesis. Additionally, several transcription factors,
   including MYB, bHLH, WD40, NAC, WRKY, bZIP and MADS, were correlated
   with the structural genes, implying their important interaction with
   anthocyanin biosynthesis-related genes. Our findings provide insight
   into anthocyanin biosynthesis and regulation patterns in L. ruthenicum
   and offer a systematic basis for elucidating the molecular mechanisms
   governing anthocyanin biosynthesis in L. ruthenicum.

Introduction

   As the largest subclass of water-soluble pigments, anthocyanins
   determine the coloration of flowers and fruits [[40]1, [41]2].
   Anthocyanins are synthesized via the flavonoid pathway and possess a
   multitude of biological roles, such as protecting plants against solar
   exposure and ultraviolet radiation, and also possess antioxidative
   capacity and free radical scavenging activity [[42]3, [43]4].
   Anthocyanins also influence dietary preferences in humans, as they have