School of Life Sciences, Key Lab of Arid and Grassland Agroecology of MOE, Lanzhou University, 222 South Tianshui Road, Lanzhou 730000, China.
Cryobiology. 2011 Oct;63(2):111-7. doi: 10.1016/j.cryobiol.2011.07.003. Epub 2011 Jul 27.
Pectin methylesterases (PMEs) are important cell wall enzymes that may play important roles in plant chilling/freezing tolerance. We investigated the possible roles of brassinosteroids (BRs) in regulation of PMEs under chilling stress. Chilling stress or 24-epibrassinolide (eBL) treatments induced significant increases in PME activity in wild type (Col-0) seedlings of Arabidopsis. The chilling-stress-induced increases in PME activity were also found in bzr1-D mutant, a BZR1 stabilized mutant with a constitutively active BR signaling pathway, but not in bri1-116, a BR insensitive null allele of the BR receptor BRI1. The results suggest that the regulation of PME activity in Arabidopsis under chilling stress depends on the BR signaling pathway. Furthermore, we showed that the effect of chilling stress on PME activity was impaired in pme41, a knockout mutant of AtPME41. Semi-quantitative RT-PCR results showed that expression of AtPME41 was induced by chilling stress in wild type plants but not in the bri1-116 mutant. The expression of AtPME41 increased in bzr1-D and eBL treated wild type seedlings, but decreased in bri1-116 seedlings. Furthermore, ion leakage induced by low temperature were dramatically increased in both bri1-116 and pme41, while lipid peroxidation was increased in bri1-116 only. The results suggest that BRs may modulate total PME activity in Arabidopsis under chilling stress by regulating AtPME41 expression. Regulation of PME activity may serve as one of the mechanisms that BR participates in chilling tolerance of plants.
果胶甲酯酶（PMEs）是重要的细胞壁酶，可能在植物耐冷/耐冻性中发挥重要作用。我们研究了油菜素内酯（BRs）在冷胁迫下调节 PMEs 的可能作用。冷胁迫或 24-表油菜素内酯（eBL）处理诱导拟南芥野生型（Col-0）幼苗中 PME 活性显著增加。在 BZR1 稳定突变体 bzr1-D 中也发现了冷胁迫诱导的 PME 活性增加，该突变体具有组成型激活的 BR 信号通路，但在 BR 受体 BRI1 的无功能 null 等位基因 bri1-116 中没有发现。结果表明，BR 信号通路决定了拟南芥在冷胁迫下 PME 活性的调节。此外，我们表明 pme41（AtPME41 的敲除突变体）对 PME 活性的冷胁迫效应受损。半定量 RT-PCR 结果表明，AtPME41 的表达在野生型植物中受到冷胁迫的诱导，但在 bri1-116 突变体中不受诱导。AtPME41 的表达在 bzr1-D 和 eBL 处理的野生型幼苗中增加，但在 bri1-116 幼苗中减少。此外，低温诱导的离子泄漏在 bri1-116 和 pme41 中均显著增加，而仅在 bri1-116 中增加脂质过氧化作用。结果表明，BRs 可能通过调节 AtPME41 的表达来调节拟南芥在冷胁迫下的总 PME 活性。PME 活性的调节可能是 BR 参与植物耐冷性的机制之一。
