| Drought stress is one of the major limitations to plant growth and development.In order to adapt to drought stress,responsive mechanism such as morphological,physiological,biochemical,cellular,and molecular levels would be activated upon plant characteristic.Dendrocalamus minor var.amoenus is an important ornamental and economic shoot bamboo specie.Besides,the bamboo was also introduced in coastal sandy area at Fujian province as a novel windbreak and dune-fixing plant species for use in mixed planting with wetland pine.But the bad planting condition and water deficit will brought adverse effect to the ornamental characteristics and benefits of the specie.Considering all above,two-year-old seedling of Dendrocalamus minor var.amoenus was used as research material to study the difference in physiology parameters and differential protein expression during natural drought stress treatments.The main study results are as follows:(1)The difference in SDS-PAGE electrophoresis gel of two kinds of protein extraction method(TCA/phenol method and PEG method)of Dendrocalamus minor var.amoenus were performed,the result shows:the differences of protein band between 5 groups of PEG method was obvious,and the whole protein was separated effectively.There were full enrichment of high abundance proteins in F3 which concentration of 16%PEG,and was the same position of two deep-color protein bands in NF(15kDa up arrow and 60kDa down arrow).However,there have no high-abundance proteins in the same region of F4 or F5.Those results suggests that total protein of Dendrocalamus minor var.amoenus could separated effectively by PEG fractionational method.(2)The difference in 2-DE electrophoresis gel of the two extraction method of Dendrocalamus minor var.amoenus leaves were performed,the result shows:the total number of detected protein in F1-F5 is more than 1700 in PEG method,but there is a certain overlap rate between adjacent groups.However,TCA/phenol method can only detect about 571 protein spots and the overlap rate between every group and NF was more than 77.9%,to reach up to 439 protein spots,which significantly improved resolution of 2-DE,indicating the PEG method is a practical and ideal protein research protocol,except for certain protein loss due to the tedious operation steps.(3)The result of variation of photosynthesic parameters during stress shows:net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)performed an significant decrease.Pn is more sensitive in response to stress than Gs and Tr.However,intercellular CO2 concentration(Ci)was showed no significantly changes in 0-15 d and then decreased later(15-26 d),reached lowest level in 26 d and then a sharp rise.But reversible,stomatal limits(Ls)showed increased firstly at days 10-26,and then decreased later.This suggested that reductions in Pn mainly resulted from stomatal limitations factors under mild drought stress period and from non-stomatal limitations factors under the severe drought stress due to PS Ⅱ structure damage and enzyme inactivation.(4)The result of variation of chlorophyll fluorescence parameters during stress shows:quantum yield(ΦOPS Ⅱ),electron transport rate(ETR)and non-photochemical quenching(qN)was significant decreased during the process of natural dehydration at days 15-30.However,the dark adapted initial minimum fluorescence(Fo)was increased significantly with the developing of drought stress.Those results elucidating that under mild stress,Dendrocalamus minor var.amoenus could maintaining function of photosynthesis apparatus through synergistic effect of reducing light harvest,heat dissipation and enzyme activity.While under severe stress,the photosynthetic electron transport and PSⅡ photosynthetic structures was inhibited or severe damaged results in repression of normal photosynthetic and metabolic pathway.(5)The result of variation of relative protective substances and enzymes during stress shows:the levels of superoxide dismutase(SOD)and catalase(CAT)was increased obviously firstly objected to short treatment period and then decreased rapidly with severe drought period.Meanwhile,the levels of proline(PRO)and malondialdehyde(MDA)was increased continuously,being significantly higher than that of the control treatment,which suggested that those protective substances and enzymes contributing to regulate activity of the protection system during the initial phase of short stress period and activity of reactive oxygen scavenging enzymes declined,leading to cell structure aggravated oxidative damage and repression of many physiological and metabolic pathways during the longer stress period.Meantime,the content of CAT was increased more than SOD,which suggests the CAT was more sensitive when object to drought.(6)The result of differential protein expression analysis during drought stress shows:there were total 41 differntially expressed proteins uncovered,among which 23 spots were up-expressed,13 spots were down-regulated,5 spots were newly-appeared.After MALDI-TOF-MS mass spectrometry identification and analysis,33 spots are identified.Besides,these proteins are related to photosynthsis,energy metabolism,stress respond. |
