Feria Ana B, Bosch Nadja, Sánchez Alfonso, Nieto-Ingelmo Ana I, de la Osa Clara, Echevarría Cristina, García-Mauriño Sofía, Monreal Jose Antonio
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Avenida Reina Mercedes no. 6, 41012, Seville, Spain.
Planta. 2016 Oct;244(4):901-13. doi: 10.1007/s00425-016-2556-9. Epub 2016 Jun 15.
Arabidopsis ppc3 mutant has a growth-arrest phenotype and is affected in phosphate- and salt-stress responses, showing that this protein is crucial under control or stress conditions. Phosphoenolpyruvate carboxylase (PEPC) and its dedicated kinase (PEPC-k) are ubiquitous plant proteins implicated in many physiological processes. This work investigates specific roles for the three plant-type PEPC (PTPC) and the two PEPC-k isoenzymes in Arabidopsis thaliana. The lack of any of the PEPC isoenzymes reduced growth parameters under optimal growth conditions. PEPC activity was decreased in shoots and roots of ppc2 and ppc3 mutants, respectively. Phosphate starvation increased the expression of all PTPC and PPCK genes in shoots, but only PPC3 and PPCK2 in roots. The absence of any of these two proteins was not compensated by other isoforms in roots. The effect of salt stress on PTPC and PPCK expression was modest in shoots, but PPC3 was markedly increased in roots. Interestingly, both stresses decreased root growth in each of the mutants except for ppc3. This mutant had a stressed phenotype in control conditions (reduced root growth and high level of stress molecular markers), but was unaffected in their response to high salinity. Salt stress increased PEPC activity, its phosphorylation state, and L-malate content in roots, all these responses were abolished in the ppc3 mutant. Our results highlight the importance of the PPC3 isoenzyme for the normal development of plants and for root responses to stress.
拟南芥ppc3突变体具有生长停滞表型，并且在磷酸盐和盐胁迫反应中受到影响，这表明该蛋白在对照或胁迫条件下至关重要。磷酸烯醇丙酮酸羧化酶（PEPC）及其专用激酶（PEPC-k）是参与许多生理过程的普遍存在的植物蛋白。这项工作研究了拟南芥中三种植物型PEPC（PTPC）和两种PEPC-k同工酶的具体作用。在最佳生长条件下，任何一种PEPC同工酶的缺失都会降低生长参数。ppc2和ppc3突变体的地上部和根中PEPC活性分别降低。磷酸盐饥饿增加了地上部所有PTPC和PPCK基因的表达，但根中仅增加了PPC3和PPCK2的表达。根中这两种蛋白中任何一种的缺失都不能被其他同工型补偿。盐胁迫对地上部PTPC和PPCK表达的影响较小，但根中PPC3明显增加。有趣的是，除了ppc3突变体之外，两种胁迫均降低了每个突变体的根生长。该突变体在对照条件下具有胁迫表型（根生长减少和胁迫分子标记水平高），但其对高盐度的反应未受影响。盐胁迫增加了根中PEPC活性、其磷酸化状态和L-苹果酸含量，ppc3突变体中所有这些反应均被消除。我们的结果突出了PPC3同工酶对植物正常发育和根对胁迫反应的重要性。
