Pacak Andrzej, Barciszewska-Pacak Maria, Swida-Barteczka Aleksandra, Kruszka Katarzyna, Sega Pawel, Milanowska Kaja, Jakobsen Iver, Jarmolowski Artur, Szweykowska-Kulinska Zofia
Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan Poznan, Poland.
Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen Copenhagen, Denmark.
Front Plant Sci. 2016 Jun 24;7:926. doi: 10.3389/fpls.2016.00926. eCollection 2016.
Phosphorus (P) in plants is taken from soil as an inorganic phosphate (Pi) and is one of the most important macroelements in growth and development. Plants actively react to Pi starvation by the induced expression of Pi transporters, MIR399, MIR827, and miR399 molecular sponge - IPS1 genes and by the decreased expression of the ubiquitin-conjugating enzyme E2 (PHOSPHATE2 - PHO2) and Pi sensing and transport SPX-MFS genes. The PHO2 protein is involved in the degradation of Pi transporters PHT1;1 (from soil to roots) and PHO1 (from roots to shoots). The decreased expression of PHO2 leads to Pi accumulation in shoots. In contrast, the pho1 mutant shows a decreased level of Pi concentration in shoots. Finally, Pi starvation leads to decreased Pi concentration in all plant tissues. Little is known about plant Pi homeostasis in other abiotic stress conditions. We found that, during the first hour of heat stress, Pi accumulated in barley shoots but not in the roots, and transcriptomic data analysis as well as RT-qPCR led us to propose an explanation for this phenomenon. Pi transport inhibition from soil to roots is balanced by lower Pi efflux from roots to shoots directed by the PHO1 transporter. In shoots, the PHO2 mRNA level is decreased, leading to an increased Pi level. We concluded that Pi homeostasis in barley during heat stress is maintained by dynamic changes in Pi-related genes expression.
植物中的磷（P）以无机磷酸盐（Pi）的形式从土壤中获取，是生长发育过程中最重要的大量元素之一。植物通过诱导Pi转运蛋白、MIR399、MIR827和miR399分子海绵-IPS1基因的表达，以及降低泛素结合酶E2（PHOSPHATE2 - PHO2）和Pi传感与转运SPX-MFS基因的表达，对Pi饥饿做出积极反应。PHO2蛋白参与Pi转运蛋白PHT1;1（从土壤到根）和PHO1（从根到地上部）的降解。PHO2表达的降低导致地上部Pi积累。相反，pho1突变体地上部的Pi浓度水平降低。最后，Pi饥饿导致所有植物组织中的Pi浓度降低。关于植物在其他非生物胁迫条件下的Pi稳态知之甚少。我们发现，在热胁迫的第一个小时内，Pi在大麦地上部积累，但在根部没有积累，转录组数据分析以及RT-qPCR使我们对这一现象提出了解释。从土壤到根的Pi转运抑制被PHO1转运蛋白引导的从根到地上部较低的Pi流出所平衡。在地上部，PHO2 mRNA水平降低，导致Pi水平升高。我们得出结论，热胁迫期间大麦中的Pi稳态是通过Pi相关基因表达的动态变化来维持的。
