Abstract

   Pear (Pyrus L.) is one of the most important temperate fruit crops
   worldwide, with considerable economic value and significant health
   benefits. Red-skinned pears have an attractive appearance and
   relatively high anthocyanin accumulation, and are especially favored by
   customers. Abnormal weather conditions usually reduce the coloration of
   red pears. The application of exogenous sucrose obviously promotes
   anthocyanins accumulation in ‘Kuerle Xiangli’ (Pyrus sinkiangensis Yü);
   however, the underlying molecular mechanism of sucrose-mediated fruit
   coloration remains largely unknown. In this study, comprehensive
   transcriptome analysis was performed to identify the essential
   regulators and pathways associated with anthocyanin accumulation. The
   differentially expressed genes enriched in Gene Ontology and the Kyoto
   Encyclopedia of Genes and Genomes items were analyzed. The transcript
   levels of some anthocyanin biosynthetic regulatory genes and structural
   genes were significantly induced by sucrose treatment. Sucrose
   application also stimulated the expression of some sugar transporter
   genes. Further RT-qPCR analysis confirmed the induction of anthocyanin
   biosynthetic genes. Taken together, the results revealed that sucrose
   promotes pear coloration most likely by regulating sugar metabolism and
   anthocyanin biosynthesis, and this study provides a comprehensive
   understanding of the complex molecular mechanisms underlying the
   coloration of red-skinned pear.

   Keywords: pear, anthocyanin accumulation, sucrose, coloration

1. Introduction

   Pear (Pyrus L.) is one of the most important fruit crops and is widely
   cultivated worldwide. It has a history of more than 3000 years in China
   [[42]1]. The annual production of pear in China reached 16.10 million
   tons and accounted for about 70% of the global total in 2020
   ([43]https://www.fao.org/faostat/en/#data/QI, accessed on 15 October
   2021). Compared with traditional green-yellow or russet pears, red
   pears generally exhibit an attractive appearance and appeal to
   consumers’ preferences [[44]2,[45]3].