Abstract
Auxin is a key phytohormone that modulates fruit formation in many fleshy fruits through the regulation of cell division and expansion. Auxin content rapidly increases after pollination and the manipulation in its levels may lead to the parthenocarpic development. ln Vitis vinifera L., little is known about the early fruit development that encompasses from pollination to fruit set. Pollination/fertilization events trigger fruit formation, and auxin treatment mimics their effect in grape berry set. However, the role of auxin in this process at the molecular level is not well understood. To elucidate the participation of auxin in grapevine fruit formation, morphological, reproductive, and molecular events from anthesis to fruit set were described in sequential days after pollination. Exploratory RNA-seq analysis at four time points from anthesis to fruit set revealed that the highest percentage of genes induced/repressed within the hormone-related gene category were auxin-related genes. Transcript profiling showed significant transcript variations in auxin signaling and homeostasis-related genes during the early fruit development. Indole acetic acid and several auxin metabolites were present during this period. Finally, application of an inhibitor of auxin action reduced cell number and the mesocarp diameter, similarly to unpollinated berries, further confirming the key role of auxin during early berry development. This work sheds light into the molecular features of the initial fruit development and highlights the auxin participation during this stage in grapevine.
Highlights
Fruit formation is a key stage with molecular, cellular, and physiological events that define the final fruit attributes
Characterization of morphological and reproductive events from pollination to fruit set Vitis vinifera cv. red globe emasculated flowers were hand-pollinated at anthesis, when flowers were receptive to pollination (Fig. S1)
Carpel/fruit samples were measured or collected at sequential time points that reflected the main processes occurring at early developmental stages, starting from 0 days after pollination (DAP), which was immediately before pollination, to fruit set at 12 DAP
Summary
Fruit formation is a key stage with molecular, cellular, and physiological events that define the final fruit attributes. Studies on the early fruit development show that hormones are key for its regulation[1,2]. Most studies in grapevine are focused on later stages of the fruit development (veraison to maturation), and information about the critical processes occurring during the early grapevine fruit development is scarce. Godoy et al Horticulture Research (2021)8:140 early reproductive events and auxin[9]. IAA levels increase as soon as 2 days after pollination (DAP), whereas gibberellin content changes later in tomato fruitlets[10]. Studies have shown a spatiotemporal control of auxin distribution during fruit formation[11,12]. Little is known about the role of auxin during the early fruit development
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