School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, 621010, Sichuan, China; Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, Hainan, China.
Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, Hainan, China.
Plant Physiol Biochem. 2021 May;162:211-220. doi: 10.1016/j.plaphy.2021.02.039. Epub 2021 Mar 1.
Fructokinase (FRK) mediates fructose phosphorylation to regulate the carbon flow and its assignment to sink tissues. Out of five HbFRKs in the genome of the rubber tree, three (HbFRK1-3) that were highly expressed in latex (cytoplasm of laticifers) were isolated and examined. According to phylogenetic analysis and intracellular location experiment, both HbFRK2 and HbFRK3 were highly possible to be expressed in cytosol, while HbFRK1 was in plastid. As the predominant isoform in laticifers, HbFRK2 had the highest transcripts, followed by HbFRK3 and HbFRK1. In enzymatic function, HbFRK2 also showed the highest affinity for fructose. To examine the roles of FRKs in latex yield and regeneration, changes in HbFRKs were examined when latex outflow from the trees were increased through two experimental interventions. In the first approach, tapping was initiated on previously untapped trees, resulting in latex yield increasing with consecutive tapping at the initial stage before it stabilized. In the second approach, latex yield from trees that were already in regular tapping was stimulated by treatment with the ethylene-based yield stimulant, ethephon. Using either method to induce an increase in latex yield, the abundance of HbFRK2 and HbFRK3 in transcripts, was increased. This development, which was especially marked in HbFRK2, may reflect a strengthening of glycolysis to meet the carbon flux and energy demands for increased rubber biosynthesis to replace rubber lost in the increased latex yield. Our results, therefore, suggest that HbFRK2 plays a critical role in fructose catabolism to facilitate rubber regeneration in the commercially exploited rubber tree.
果糖激酶 (FRK) 介导果糖磷酸化，以调节碳流及其在汇组织中的分配。在橡胶树基因组中的 5 个 HbFRKs 中，有 3 个（HbFRK1-3）在乳胶（乳汁管的细胞质）中高度表达，被分离并进行了研究。根据系统发育分析和细胞内定位实验，HbFRK2 和 HbFRK3 很可能在细胞质中表达，而 HbFRK1 则在质体中表达。作为乳汁管中的主要同工型，HbFRK2 的转录本最高，其次是 HbFRK3 和 HbFRK1。在酶学功能方面，HbFRK2 对果糖也表现出最高的亲和力。为了研究 FRKs 在乳胶产量和再生中的作用，通过两种实验干预观察了 HbFRKs 的变化，以增加树体中的乳胶流出量。在第一种方法中，对以前未打孔的树木进行打孔，结果导致乳胶产量在初始阶段随着连续打孔而增加，然后稳定下来。在第二种方法中，用乙烯基产胶刺激剂乙膦处理已经进行常规打孔的树木，刺激乳胶产量。通过这两种方法中的任何一种来诱导乳胶产量的增加，HbFRK2 和 HbFRK3 的转录本丰度都会增加。这种变化在 HbFRK2 中尤为明显，可能反映了糖酵解的加强，以满足增加的橡胶生物合成所需的碳通量和能量需求，以替代增加的乳胶产量中损失的橡胶。因此，我们的研究结果表明，HbFRK2 在果糖分解代谢中发挥关键作用，有助于商业开发的橡胶树中橡胶的再生。
