Seed Development in a Stenospermocarpic Grape with Edible Seeds

Grape is one of the most important fruit crops worldwide. It has been used as table fruit as well as for making wine and grape products such as juice, jelly, vinegar, raisins, and seed oils. In this study, we investigated the seed structure of a stenospermocarpic grape with edible seeds and compared it with that of seeded grapes. Seeds of a stenospermocarpic grape ‘Hongju Seedless’, which is one of the offspring of a cross between ‘Perlon’ and ‘Italia’, had thin layered medium integument tissue. In contrast, seeds of seeded grapes ‘Italia’ and ‘Campbell Early’ had thick medium integument tissue that was comprised of several lignified cell layers. Lignification of medium integument tissue of seeded grapes progressed gradually until 42 days after flowering. We examined the expression profiles of lignin biosynthesis-related genes during grape development using RNA sequencing of berries or seeds. Twelve transcription factors in lignification regulatory networks were selected and their expression patterns were characterized in detail. This study will provide a developmental genomic basis for grape biology and breeding.