Low-glutathione mutants are impaired in growth but do not show an increased sensitivity to moderate water deficit

Glutathione is considered a key metabolite for stress defense and elevated levels have frequently been proposed to positively influence stress tolerance. To investigate whether glutathione affects plant performance and the drought tolerance of plants, wild-type Arabidopsis plants and an allelic series of five mutants (rax1, pad2, cad2, nrc1, and zir1) with reduced glutathione contents between 21 and 63% compared to wild-type glutathione content were phenotypically characterized for their shoot growth under control and water-limiting conditions using a shoot phenotyping platform. Under non-stress conditions the zir1 mutant with only 21% glutathione showed a pronounced dwarf phenotype. All other mutants with intermediate glutathione contents up to 62% in contrast showed consistently slightly smaller shoots than the wild-type. Moderate drought stress imposed through water withdrawal until shoot growth ceased showed that wild-type plants and all mutants responded similarly in terms of chlorophyll fluorescence and growth retardation. These results lead to the conclusion that glutathione is important for general plant performance but that the glutathione content does not affect tolerance to moderate drought conditions typically experienced by crops in the field.

谷胱甘肽（Glutathione）被视为植物胁迫防御的关键代谢物，其含量升高常被报道可正向提升胁迫耐受性。为探究谷胱甘肽是否会影响植物生长表现与植物耐旱性，研究人员以野生型拟南芥（Arabidopsis）以及5株谷胱甘肽含量仅为野生型21%~63%的等位系列突变体（rax1、pad2、cad2、nrc1、zir1）为材料，借助地上部表型分析平台，在正常对照与水分限制条件下对其地上部生长开展表型鉴定。在非胁迫对照条件下，谷胱甘肽含量仅为野生型21%的zir1突变体呈现出显著矮化表型；其余谷胱甘肽含量介于22%~62%的突变体，其地上部均始终略小于野生型植株。通过停止供水施加中度干旱胁迫直至地上部生长停滞，研究发现野生型植株与所有突变体在叶绿素荧光参数与生长抑制程度上均表现出相似响应。上述结果表明，谷胱甘肽对植物的整体生长表现具有重要作用，但谷胱甘肽含量并不会影响作物在田间通常遭遇的中度干旱胁迫耐受性。