Department of Entomology, The Pennsylvania State University, University Park, PA, United States of America.
PLoS One. 2023 Nov 27;18(11):e0289143. doi: 10.1371/journal.pone.0289143. eCollection 2023.
To defend against damage from environmental stress, plants have evolved strategies to respond to stress efficiently. One such strategy includes forming mutualist relationships with endophytes which confer stress-alleviating plant defensive and growth promoting effects. Metarhizium robertsii is an entomopathogen and plant-protective and growth-promoting endophyte. To determine the context dependency of the relationship between M. robertsii and maize, we conducted a greenhouse experiment that imposed stress as deficit and excess soil moisture on maize plants which were inoculated or not inoculated with M. robertsii and measured plant growth and defense indicators. Maize height and endophytic root colonization by M. robertsii were positively correlated in the deficit water treatment, but not in the adequate or excess water treatments. The relative expression of ZmLOX1 in the jasmonic acid (JA) biosynthesis pathway was significantly greater in M. robertsii-inoculated than in non-inoculated plants, but water treatment had no effect. There was significant interaction between M. robertsii and water treatments on foliar concentrations of JA and jasmonoyl isoleucine (JA-ILE), suggesting that water stress impacts M. robertsii as a modulator of plant defense. Water stress, but not inoculation with M. robertsii, had a significant effect on the expression of MYB (p = 0.021) and foliar concentrations of abscisic acid (p<0.001), two signaling molecules associated with abiotic stress response. This study contributes toward understanding the highly sophisticated stress response signaling network and context dependency of endophytic mutualisms in crops.
为了抵御环境胁迫造成的损伤，植物进化出了高效响应胁迫的策略。其中一种策略是与内生真菌形成互利共生关系，从而赋予植物缓解胁迫的防御和促进生长的效应。玫烟色棒束孢是一种昆虫病原真菌和植物保护及促生内生真菌。为了确定玫烟色棒束孢与玉米之间关系的情境依赖性，我们进行了一项温室实验，对接种或未接种玫烟色棒束孢的玉米植株施加土壤水分亏缺和过量胁迫，并测量了植物生长和防御指标。在水分亏缺处理中，玉米株高与玫烟色棒束孢的内生根定殖呈正相关，但在水分充足或过量处理中则没有相关性。茉莉酸（JA）生物合成途径中 ZmLOX1 的相对表达在接种了玫烟色棒束孢的植株中显著高于未接种的植株，但水分处理没有影响。在 JA 和茉莉酰异亮氨酸（JA-ILE）的叶部浓度方面，玫烟色棒束孢与水分处理之间存在显著的互作，表明水分胁迫影响了玫烟色棒束孢作为植物防御的调节剂。水分胁迫，而不是接种玫烟色棒束孢，对 MYB（p=0.021）的表达和脱落酸（ABA）的叶部浓度（p<0.001）有显著影响，这两种信号分子与非生物胁迫响应有关。本研究有助于理解作物内生共生关系的高度复杂胁迫响应信号网络和情境依赖性。
