Stone Cell Development in Pear

Abstract

Pear (Pyrus spp.) is one of the most important deciduous fruit trees grown in the world. The genus Pyrus belongs to the subfamily Pomoideae of the family Rosaceae. Stone cells (sclereids), heavily lignified cells present in fruit flesh, serve as a distinctive trait of pear fruits. Stone cells are characterized by thickening and lignified cell walls, and their development is closely associated with lignin metabolism. The content and size of stone cell clusters are among the key factors in determining the internal quality of pear fruits. Not only are stone cells critically involved in fruit texture, but they are also closely associated with the overall flavor of pear fruits. Therefore, regulation of the size and content of stone cell clusters is key for improving fruit quality, and in promoting expansion of the pear industry. In this review, effects of stone cells on fruit quality, including texture, flavor, and response to disease, as well as the mechanism of stone cell development in pear fruits, including morphological characteristics, distribution, development, components, formation, and regulation mechanism, will be presented. Moreover, molecular mechanisms of pear lignin metabolism, including pear lignin monomers type, biosynthesis pathway, and identification of key gene families will be also summarized. Finally, we will share some ideas relevant to future research directions pertaining to stone cells in pear.