Faculty of Science, Department of Biology, Ege University, Bornova-Izmir, 35100, Türkiye.
BMC Plant Biol. 2024 Sep 16;24(1):864. doi: 10.1186/s12870-024-05503-9.
High GABA levels and its conversion to succinate via the GABA shunt are known to be associated with abiotic and biotic stress tolerance in plants. The exact mode of action is still under debate and it is not yet clear whether GABA is a common component of the plant stress defense process or not. We hypothesized that if it is a common route for stress tolerance, activation of GABA-shunt by a biotic stressor might also function in increased abiotic stress tolerance. To test this, Brassica napus plants treated with Flagellin-22 (Flg-22) were exposed to drought stress and the differences in GABA levels along with GABA-shunt components (biosynthetic and catabolic enzyme activities) in the leaf and root samples were compared. In order to provide a better outlook, MYC2, MPK6 and ZAT12, expression profiles were also analyzed since these genes were recently proposed to function in abiotic and biotic stress tolerance.
Briefly, we found that Flg treatment increased drought stress tolerance in B. napus via GABA-shunt and the MAPK cascade was involved while the onset was different between leaves and roots. Flg treatment promoted GABA biosynthesis with increased GABA content and GAD activity in the leaves. Better performance of the Flg treated plants under drought stress might be dependent on the activation of GABA-shunt which provides succinate to TCA since GABA-T and SSADH activities were highly induced in the leaves and roots. In the transcript analysis, Flg + drought stressed groups had higher MYC2 transcript abundances correlated well with the GABA content and GABA-shunt while, MPK6 expression was induced only in the roots of the Flg + drought stressed groups. ZAT12 was also induced both in leaves and roots as a result of Flg-22 treatment. However, correlation with GABA and GABA-shunt could be proposed only in Flg + drought stressed group.
We provided solid data on how GABA-shunt and Fgl-22 are interacting against abiotic stress in leaf and root tissues. Fgl-22 induced ETI activated GABA-shunt with a plausible cross talk between MYC2 and ZAT12 transcription factors for drought stress tolerance in B. napus.
已知高水平的 GABA 及其通过 GABA 分流转化为琥珀酸与植物的非生物和生物胁迫耐受性有关。确切的作用机制仍存在争议，目前尚不清楚 GABA 是否是植物应激防御过程的共同组成部分。我们假设如果 GABA 是耐受应激的共同途径，那么生物胁迫因子对 GABA 分流的激活也可能在提高非生物胁迫耐受性方面发挥作用。为了验证这一点，用鞭毛蛋白-22（Flg-22）处理拟南芥植物，然后将其暴露于干旱胁迫下，并比较叶片和根样本中 GABA 水平以及 GABA 分流成分（生物合成和分解代谢酶活性）的差异。为了提供更好的前景，还分析了 MYC2、MPK6 和 ZAT12 的表达谱，因为这些基因最近被提出在非生物和生物胁迫耐受性中发挥作用。
简要地说，我们发现 Flg 通过 GABA 分流增加了油菜的干旱胁迫耐受性，而 MAPK 级联反应参与其中，叶片和根之间的起始时间不同。Flg 处理促进了叶片中 GABA 的生物合成，增加了 GABA 含量和 GAD 活性。Flg 处理植物在干旱胁迫下的更好表现可能依赖于 GABA 分流的激活，因为 GABA-T 和 SSADH 活性在叶片和根中高度诱导，从而为 TCA 提供琥珀酸。在转录分析中，Flg + 干旱胁迫组的 MYC2 转录丰度较高，与 GABA 含量和 GABA 分流密切相关，而 MPK6 表达仅在 Flg + 干旱胁迫组的根中诱导。ZAT12 也因 Flg-22 处理而在叶片和根中均被诱导。然而，仅在 Flg + 干旱胁迫组中可以提出与 GABA 和 GABA 分流的相关性。
我们提供了关于 GABA 分流和 Flg-22 如何在叶片和根组织中相互作用抵抗非生物胁迫的可靠数据。Flg-22 诱导 ETI 激活 GABA 分流，可能存在 MYC2 和 ZAT12 转录因子之间的交叉对话，以提高油菜对干旱胁迫的耐受性。
