Abstract
BackgroundBlueberry (Vaccinium spp.) is characterized by the production of berries that are smaller than most common fruits, and the underlying mechanisms of fruit size in blueberry remain elusive. V. corymbosum ‘O’Neal’ and ‘Bluerain’ are commercial southern highbush blueberry cultivars with large- and small-size fruits, respectively, which mature ‘O’Neal’ fruits are 1 ~ 2-fold heavier than those of ‘Bluerain’. In this study, the ontogenetical patterns of ‘O’Neal’ and ‘Bluerain’ hypanthia and fruits were compared, and comparative transcriptomic analysis was performed during early fruit development.ResultsV. corymbosum ‘O’Neal’ and ‘Bluerain’ hypanthia and fruits exhibited intricate temporal and spatial cell proliferation and expansion patterns. Cell division before anthesis and cell expansion after fertilization were the major restricting factors, and outer mesocarp was the key tissue affecting fruit size variation among blueberry genotypes. Comparative transcriptomic and annotation analysis of differentially expressed genes revealed that the plant hormone signal transduction pathway was enriched, and that jasmonate-related TIFYs genes might be the key components orchestrating other phytohormones and influencing fruit size during early blueberry fruit development.ConclusionsThese results provided detailed ontogenetic evidence for determining blueberry fruit size, and revealed the important roles of phytohormone signal transductions involving in early fruit development. The TIFY genes could be useful as markers for large-size fruit selection in the current breeding programs of blueberry.
Highlights
Blueberry (Vaccinium spp.) is characterized by the production of berries that are smaller than most common fruits, and the underlying mechanisms of fruit size in blueberry remain elusive
FW2.2, the first isolated quantitative trait locus from S. lycopersicum, contributes to approximately 30% of fruit weight variation by negatively regulating cell division [2, 12]; the highest difference in FW2.2 transcript abundance between Vaccinium corymbosum cultivars with large and small-size fruits was not occurred during flower bud enlargement and early fruit development, indicating that complex mechanisms are involved in blueberry fruit development and fruit size/weight variation [17]
Comparative transcriptomic analysis was performed in these cultivars during anthesis and early fruit development. These results provide detailed ontogenetic evidence for the spatiotemporal patterns of cell proliferation and expansion and help to identify potential genes involved in regulating blueberry fruit size/weight
Summary
Blueberry (Vaccinium spp.) is characterized by the production of berries that are smaller than most common fruits, and the underlying mechanisms of fruit size in blueberry remain elusive. Final fruit size/weight is determined by cell proliferation and expansion, which is involved in successive processes of floral meristem, gynoecium formation, pollination and fertilization, locule and seed formation, as well as fruit growth and development [2, 5,6,7]. FW2.2 (fruit weight 2.2), the first isolated quantitative trait locus from S. lycopersicum, contributes to approximately 30% of fruit weight variation by negatively regulating cell division [2, 12]; the highest difference in FW2.2 transcript abundance between Vaccinium corymbosum cultivars with large and small-size fruits was not occurred during flower bud enlargement and early fruit development (the fastest stages for cell proliferation), indicating that complex mechanisms are involved in blueberry fruit development and fruit size/weight variation [17]. Identifying more regulators and their biological functions will help us to further interpret the fundamental mechanisms of fruit size/weight as well as develop practical applications to control these traits
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