Sutton Mary, Roussel Bayleigh, Chavez Dario J, Malladi Anish
Department of Horticulture, University of Georgia, Athens, GA, United States.
Department of Horticulture, University of Georgia, Griffin, GA, United States.
Front Plant Sci. 2023 Apr 20;14:1155755. doi: 10.3389/fpls.2023.1155755. eCollection 2023.
Early fruit growth in peach is characterized by cell production. Cytokinins have established roles in regulating cell division and may regulate cell production during early fruit growth. However, the role of active cytokinins and regulation of their metabolism are not well characterized in the peach fruit. In this study, fruit growth parameters, concentrations of active cytokinin bases and a cytokinin riboside, and expression of three key cytokinin metabolism-related gene families were determined during early fruit growth. Early fruit growth was associated with intensive cell production until around 40 days after full bloom. During the early stages of this period, -zeatin (Z), isopentenyladenine (iP), dihydrozeatin (DHZ) and Z-riboside (ZR), displayed higher abundance which declined rapidly by 3.5- to 16-fold during the later stages. Changes in concentration of active cytokinin bases were consistent with roles for them in regulating cell production. Expression analyses of members of cytokinin biosynthesis-related gene families, () and (), further indicated that mechanisms of synthesis of cytokinin metabolites and their activation are functional within the fruit pericarp. Changes in expression of multiple members of the family paralleled changes in active cytokinin concentrations. Specifically, transcript abundance of and were correlated with concentrations of Z, and iP and DHZ, respectively, suggesting that the direct activation pathway is an important route for active cytokinin base synthesis during early fruit development. Transcript abundance of two () genes, and , was consistent with roles in cytokinin catabolism during later stages of early fruit growth. Together, these data support a role for active cytokinins synthesized in the fruit pericarp in regulating early fruit growth in peach.
桃果实早期生长的特点是细胞增殖。细胞分裂素在调节细胞分裂方面具有既定作用，可能在果实早期生长过程中调节细胞增殖。然而，活性细胞分裂素的作用及其代谢调控在桃果实中尚未得到充分表征。在本研究中，测定了果实早期生长期间的果实生长参数、活性细胞分裂素碱基和一种细胞分裂素核糖苷的浓度，以及三个与细胞分裂素代谢相关的关键基因家族的表达情况。果实早期生长与旺盛的细胞增殖相关，直至盛花后约40天。在此期间的早期阶段，玉米素（Z）、异戊烯腺嘌呤（iP）、二氢玉米素（DHZ）和Z - 核糖苷（ZR）含量较高，而在后期迅速下降了3.5至16倍。活性细胞分裂素碱基浓度的变化与其在调节细胞增殖中的作用一致。对细胞分裂素生物合成相关基因家族成员的表达分析进一步表明，细胞分裂素代谢产物的合成及其激活机制在果实果皮中发挥作用。细胞分裂素氧化酶/脱氢酶（CKX）家族多个成员的表达变化与活性细胞分裂素浓度的变化平行。具体而言，CKX3和CKX5的转录丰度分别与Z、iP和DHZ的浓度相关，这表明直接激活途径是果实早期发育过程中活性细胞分裂素碱基合成的重要途径。两个细胞色素P450（CYP735A）基因CYP735A1和CYP735A2的转录丰度与果实早期生长后期细胞分裂素分解代谢中的作用一致。总之，这些数据支持果实果皮中合成的活性细胞分裂素在调节桃果实早期生长中的作用。
