水分胁迫下发草(Deschampsia caespitosa)叶片脯氨酸及其代谢产物变化

Analyses of proline accumulation and metabolism in the leaves of Deschampsia caespitosa under drought and waterlogging stress

以发草(Deschampsia caespitosa)为供试材料,通过盆栽模拟水分胁迫,研究重度干旱、中度干旱、轻度干旱、植物正常需水量(对照)、轻度水涝、中度水涝、重度水涝处理下发草叶片脯氨酸(Pro)积累状况及其代谢途径中底物、中间产物和关键酶的动态变化,以期从脯氨酸代谢途径对发草抗旱/涝机理进行初步探讨。结果显示,干旱和水涝胁迫前期发草叶片Pro含量显著升高,谷氨酸(Glu)和鸟氨酸(Orn)含量显著下降,Δ^(1)-吡咯琳-5-羧酸合成酶(P5CS)活性、鸟氨酸转氨酶(δ-OAT)活性、Δ^(1)-吡咯琳-5-羧酸还原酶(P5CR)活性均显著增强,而脯氨酸脱氢酶(ProDH)活性显著降低,表明干旱和水涝胁迫前期发草叶片通过脯氨酸合成代谢的加强和分解代谢的抑制共同积累脯氨酸,以缓解干旱和水涝胁迫产生的危害,Glu途径和Orn途径协同作用于叶片脯氨酸合成代谢过程。中度、轻度干旱和轻度水涝处理21 d后Pro含量趋于稳定,持续21 d的重度干旱处理和持续28 d的重度水涝处理时发草死亡,共同显示了发草对水涝和干旱具有较强的耐受性。结论为高寒沼泽湿地旱涝“共耐性”植物的研究提供理论基础,同时为利用发草开展退化高寒沼泽湿地植被恢复提供科学依据。

Deschampsia caespitosa has the characteristics of cold resistance and pruning resistance.They can grow not only in arid environments such as grassland,but also in wet habitats such as river beach and swamp.D.caespitosa has high seed yield and high germination rate.It is one of the ideal species for vegetation restoration in the alpine marshes.Water is one of the important abiotic factors limiting many aspects of plant growth and development,including survival,metabolism,and geographical distributions.Water deficit is the most common stress factor during growth and development.Plants have evolved an effective antioxidant system to remove excess reactive oxygen species to protect them from damage.Proline(Pro),a widely distributed osmotic regulator,plays an important role in preventing plants from damage under water stress.In order to study the physiological mechanism of D.caespitosa growth under drought and flood stress,we examined Pro accumulation and metabolism in the leaves of D.caespitosa to understand how this herbage plant tolerates drought and waterlogging stress in the alpine marshes.We analyzed Pro accumulation and changes of the substrate,intermediate products and enzyme activities in the Pro metabolism under drought and waterlogging stress.We found that the Pro content was increased in the leaves of D.caespitosa under drought stress and waterlogging stress.Pro levels were increased over the period of treatment but were leveled off or decreased after treatment for 21 days.Glutamate(Glu)and ornithine(Orn)levels were decreased in the leaves of D.caespitosa under drought stress and waterlogging stress,while Glu was changed more obviously.Glu and Orn were involved in Pro metabolism that leading to Pro production.The levels of glutamic-γ-semialdehyde(GSA)andΔ^(1)-pyrroline-5-carboxylate(P5C),intermediates of the Pro metabolism,changed under water stress.The activities ofΔ^(1)-pyrroline-5-carboxylic acid synthetase(P5CS),ornithine aminotransferase(δ-OAT),andΔ^(1)-pyrroline-5-carboxylic acid reductase(P5CR)were increased,while the activity of proline dehydrogenase(ProDH)was reduced.Osmotic stress was alleviated in the leaves of D.caespitosa by increasing Pro content.Pro increase was caused by the active Pro accumulation and the interaction of the Glu pathway and Orn pathway.Pro accumulation was enhanced by Pro anabolism and inhibited by Pro catabolism.D.caespitosa was died after the severe drought treatment for 21 days and severe waterlogging treatment for 28 days.Our results are helpful for future in-depth study of plant co-tolerance to drought and flood stress in alpine marshes as well as for the restoration of the degraded alpine marshes with herbage plants.