| Temperature plays a vital role in the process of plant growth and development,low temperature stress reduced the yield and quality of plants.Low temperature stress can cause plant stomatal conductance and photosynthesis declined,energy production and material synthesis hampered,consumption enhanced,affecting the normal growth and development of plants seriously.Puccinellia tenuiflora is a monoeotyledonous gramineae perennial species,mainly distributed in songnen plain in northeast China,with strong cold resistance.P.tenuiflora is soft and good palatability,high protein content,is an excellent forage.So,in this study,P.tenuiflora leaves as materials,we use combined physiological and proteomic approach to investigate the molecular mechanisms of P.tenuiflora seedings under chilling stress(10? for 10 d and 20 d),providing theoretical basis for increasing the production of P.tenuiflora.Physiological results indicated that relative water content decreased,the chlorophyll content and photosynthetic rate also decreased,chilling inhibited the photosynthesis and affected the growth of P.tenuiflora seedlings.The increase of malondialdehyde and relative electrolyte leakage suggested the membrane structure stability of P.tenuiflora was damaged.However,a large number of accumulation of proline,soluble sugar,and glycine betaine,maintain the osmotic balance,and protect the integrity of the membrane structure.The increase of formation rate of O2-and hydrogen peroxide content indicated that reactive oxygen species(ROS)accumulation,and more ROS generation with the extension of chilling treatment time,cause oxidative stress aggravate.The activity of ascorbic acid peroxidase(APX)and the other antioxidant enzymes increased,and the content of antioxidants also increased sharply,these enhance the oxidative defense capability of P.tenuiflora.Proteomics results showed that we obtained 107 reproducibly matched spots showed differential expression in abundance.After submitted to MALDI-TOF-TOF MS for identification,104 spots were identified.Among them,a total of 12 spots were identified under chilling stress for 10 d and 20 d,40 spots were identified under chilling stress for 10 d,52 spots were identified under chilling stress for 20 d.These proteins were mainly involved in light reaction,the Calvin cycle,carbohydrates and energy metabolism,stress and defense,protein synthesis,protein processing and transport,protein degradation,metabolism,membrane and transport process and so on.We found that the expression levels all decreased of proteins,that participate in light reaction,carbohydrates and energy metabolism,protein synthesis,and protein expression levels were increased,which participate in protein degradation.Combined with physiology and proteomics results,we can conclude that the P.tenuiflora seedlings response to chilling stress through the folloxving mechanisms:(1)chlorophyll contents declined,protein expression levels of coproporphyrinogen ? oxidase(CPOX),chlorophyll a/b-binding protein(CAB),and oxygen-evolving enhancer protein(OEE)decreased,these can reduce the absorption of light energy in P.tenuiflora leaves,reducing accumulation of excessive light energy and molecular oxygen in P.tenuiflora;(2)the activity of antioxidant enzymes,such as APX,glutathione reductase(GR),glutathione peroxidase(GPX),glutathione S-transferase(GST)increased,antioxidant contents,AsA and glutathione(GSH)such as a sharp increase in reducing oxidative damage caused by chilling stress;(3)metabolism related enzyme,such as thiamine biological synthetase involved in the metabolism of thiamine,expression level increased,also can participate in the P.tenuiflora response to oxidative stress caused by chilling stress;(4)through rapid accumulation of osmotic protection substances in P.tenuiflora leaves,such as proline,soluble sugar and glycine betaine.not only to ease the osmotic stress,can also be used to remove ROS,maintain the stability of protein structure.This research provides important foundation for improving cold tolerance of Gramineae. |
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