Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma, USA.
Plant Cell Environ. 2013 Mar;36(3):706-20. doi: 10.1111/pce.12008. Epub 2012 Oct 3.
Drought and tropospheric ozone are escalating climate change problems that can co-occur. In this study, we observed Medicago truncatula cultivar Jemalong that is sensitive to ozone and drought stress when applied singly, showed tolerance when subjected to a combined application of these stresses. Lowered stomatal conductance may be a vital tolerance mechanism to overcome combined ozone and drought. Sustained increases in both reduced ascorbate and glutathione in response to combined stress may play a role in lowering reactive oxygen species and nitric oxide toxicity. Transcriptome analysis indicated that genes associated with glucan metabolism, responses to temperature and light signalling may play a role in dampening ozone responses due to drought-induced stomatal closure during combined occurrence of these two stresses. Gene ontologies for jasmonic acid signalling and innate immunity were enriched among the 300 differentially expressed genes unique to combined stress. Differential expression of transcription factors associated with redox, defence signalling, jasmonate responses and chromatin modifications may be important for evoking novel gene networks during combined occurrence of drought and ozone. The alterations in redox milieu and distinct transcriptome changes in response to combined stress could aid in tweaking the metabolome and proteome to annul the detrimental effects of ozone and drought in Jemalong.
干旱和对流层臭氧是正在加剧的气候变化问题，它们可能同时发生。在这项研究中，我们观察到苜蓿栽培品种 Jemalong 对单独施加的臭氧和干旱胁迫敏感，但当同时施加这些胁迫时表现出耐受性。降低的气孔导度可能是一种重要的耐受机制，以克服联合的臭氧和干旱胁迫。响应联合胁迫，还原型谷胱甘肽和抗坏血酸持续增加，可能在降低活性氧和一氧化氮毒性方面发挥作用。转录组分析表明，与葡聚糖代谢、对温度和光照信号的反应相关的基因可能在这两种胁迫同时发生时，由于干旱引起的气孔关闭，在减轻臭氧反应方面发挥作用。在联合胁迫特有的 300 个差异表达基因中，富集了茉莉酸信号和先天免疫的基因本体论。与氧化还原、防御信号、茉莉酸反应和染色质修饰相关的转录因子的差异表达可能对于在干旱和臭氧同时发生时引发新的基因网络很重要。氧化还原环境的改变和对联合胁迫的独特转录组变化可能有助于调整代谢组和蛋白质组，以消除臭氧和干旱对 Jemalong 的不利影响。
