Koochak Haniyeh, Ludwig-Müller Jutta
Institut für Botanik, Technische Universität Dresden, 01062 Dresden, Germany.
Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-5910, USA.
Plants (Basel). 2021 Jul 8;10(7):1398. doi: 10.3390/plants10071398.
Salt stress is among the most challenging abiotic stress situations that a plant can experience. High salt levels do not only occur in areas with obvious salty water, but also during drought periods where salt accumulates in the soil. The moss became a model for studying abiotic stress in non-vascular plants. Here, we show that high salt concentrations can be tolerated in vitro, and that auxin homeostasis is connected to the performance of under these stress conditions. The auxin levels can be regulated by conjugating IAA to amino acids by two members of the family of GH3 protein auxin amino acid-synthetases that are present in . Double gene knock-out mutants were more tolerant to high salt concentrations. Furthermore, free IAA levels were differentially altered during the time points investigated. Since, among the mutant lines, an increase in IAA on at least one NaCl concentration tested was observed, we treated wild type (WT) plants concomitantly with NaCl and IAA. This experiment showed that the salt tolerance to 100 mM NaCl together with 1 and 10 µM IAA was enhanced during the earlier time points. This is an additional indication that the high IAA levels in the double GH3-KO lines could be responsible for survival in high salt conditions. While the high salt concentrations induced several selected stress metabolites including phenols, flavonoids, and enzymes such as peroxidase and superoxide dismutase, the GH3-KO genotype did not generally participate in this upregulation. While we showed that the GH3 double KO mutants were more tolerant of high (250 mM) NaCl concentrations, the altered auxin homeostasis was not directly involved in the upregulation of stress metabolites.
盐胁迫是植物可能遭遇的最具挑战性的非生物胁迫情况之一。高盐水平不仅出现在有明显咸水的地区，也出现在干旱时期，此时盐分在土壤中积累。苔藓成为研究非维管植物非生物胁迫的模型。在这里，我们表明高盐浓度在体外是可以耐受的，并且生长素稳态与在这些胁迫条件下的表现相关。生长素水平可以通过GH3蛋白生长素氨基酸合成酶家族的两个成员将吲哚-3-乙酸（IAA）与氨基酸结合来调节，它们存在于[具体植物名称未给出]中。双基因敲除突变体对高盐浓度更耐受。此外，在研究的时间点，游离IAA水平发生了不同的变化。由于在突变体系中，在至少一个测试的NaCl浓度下观察到IAA增加，我们同时用NaCl和IAA处理野生型（WT）植物。该实验表明，在早期时间点，对100 mM NaCl以及1和10 μM IAA的耐盐性增强。这进一步表明双GH3基因敲除系中高IAA水平可能是在高盐条件下存活的原因。虽然高盐浓度诱导了几种选定的胁迫代谢产物，包括酚类、黄酮类以及过氧化物酶和超氧化物歧化酶等酶，但GH3基因敲除基因型一般不参与这种上调。虽然我们表明GH3双基因敲除突变体对高（250 mM）NaCl浓度更耐受，但生长素稳态的改变并未直接参与胁迫代谢产物的上调。
