French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev - Sede Boqer Campus, Midreshet Ben-Gurion, Israel.
Plant Cell Environ. 2019 Jun;42(6):1897-1912. doi: 10.1111/pce.13522. Epub 2019 Mar 8.
Solar irradiance and air temperature are characterized by dramatic circadian fluctuations and are known to significantly modulate fruit composition. To date, it remains unclear whether the abrupt, yet predictive, diurnal changes in radiation and temperature prompt direct metabolic turn-over in the fruit. We assessed the role of fruit insolation, air temperature, and source-tissue CO assimilation in the diurnal compositional changes in ripening grape berries. This was performed by comparing the diurnal changes in metabolite profiles of berries positioned such that they experienced (a) contrasting diurnal solar irradiance patterns, and (b) similar irradiance but contrasting diurnal CO assimilation patterns of adjacent leaves. Grape carbon levels increased during the morning and decreased thereafter. Sucrose levels decreased throughout the day and were correlated with air temperature, but not with the diurnal pattern of leaf CO assimilation. Tight correlation between sucrose and glucose-6-phosphate indicated the involvement of photorespiration/glycolysis in sucrose depletion. Amino acids, polyamines, and phenylpropanoids fluctuated diurnally, and were highly responsive to the diurnal insolation pattern of the fruit. Our results fill the knowledge gap regarding the circadian pattern of source-sink assimilate-translocation in grapevine. In addition, they suggest that short-term direct solar exposure of the fruit impacts both its diurnal and nocturnal metabolism.
太阳辐照度和空气温度具有明显的昼夜波动特征，已知它们会显著调节果实成分。迄今为止，尚不清楚辐射和温度的这种突然但可预测的昼夜变化是否会促使果实发生直接的代谢转换。我们评估了果实光照、空气温度和源组织 CO 同化在成熟葡萄浆果昼夜组成变化中的作用。这是通过比较浆果代谢物谱的昼夜变化来实现的，这些浆果的位置使得它们经历了（a）相反的昼夜太阳辐照度模式，和（b）相邻叶片相似的辐照度但相反的昼夜 CO 同化模式。葡萄碳水平在上午增加，此后减少。蔗糖水平全天下降，并与空气温度相关，但与叶片 CO 同化的昼夜模式无关。蔗糖与葡萄糖-6-磷酸之间的紧密相关性表明光合作用/糖酵解参与了蔗糖的消耗。氨基酸、多胺和苯丙烷类物质昼夜波动，对果实的昼夜光照模式高度敏感。我们的研究结果填补了葡萄藤源库同化物转运的昼夜模式的知识空白。此外，它们表明，果实的短期直接太阳暴露会影响其昼夜代谢。
