Proteomic Analysis Of Four Coniferous Tree Species And Populus×euramericana Cv. '74/76' Under Drought And High-temperature Stress

The global warming predicted in future will produce an increased probability of droughtand high-temperature episodes, larger vapor-pressure deficits and in general more frequent andmore severe extreme climatic events. The counterbalancing effects of increasing water deficitand temperature, which usually occur together in many regions under recent climatic warming,are the main factors expected to influence forest production, and to limit the growth of foresttree species. Thus, understanding the genetic basis and molecular mechanisms of drought andhigh-temperature stress adaptation is of particular importance for forest tree species given thepossibility of future rapid climatic changes. Elucidation of the response mechanisms in treespecies will permit development of biochemical and molecular indicators to identify and selectfor genotypes tolerant of drought and high-temperature during breeding programmes. Inaddition, the information could be useful for the management of genetic resources and for thegenetic improvement of drought and high-temperature stress tolerance in cultivated forest treespecies.In this paper, to provide an insight into drought and high-temperature tolerant tree speciesselection, proteins responding to drought and high-temperature stress in four coniferous treespecies (Pinus armandi Franch., Pinus tabulaeformis Carr., Pinus bungeana Zucc.ex Endl. andPinus sylvestris L.var.mongolica Litv.) were studied using proteomics technique based on ourprevious research work. Also, we studied the stress proteins of Pinus armandi Franch andPopulus×euramericana cv. '74/76' to drought and high-temperature using the techniquementioned above. We discussed the difference of proteins produced by these two kinds ofstress in investigated broadleaved and coniferous tree species, aimed at providing molecularbasis and difference of needle-leaved and broadleaved tree species responding to drought andhigh-temperature stress, and providing the first data for cross adaptation and resistantconsistency.Based on the established sucrose extraction method of needle protein, 342 proteinsseparated with 2-dimensional electrophoresis (2-DE) from the four coniferous tree specieswere analyzed by UPGMA cluster system, and the genetic distance varied from 0.07 to 0.12.UPGMA cluster analysis indicated that the four coniferous tree species were classified intothree groups when genetic distance varied from 0.07 to 0.087. The genetic similaritycoefficient between P. bungeana Zucc.ex Endl. and P. armandi Franch., P. tabulaeformis Carr,P. sylvestris L.var.mongolica Litv. was 0.78, 0.84, 0.85, respectively. It suggested that the genetic relation between P. bungeana Zucc.ex Endl. and P. armandi Franch.was farther thanthat between P. bungeana Zucc.ex Endl. and another two. The result was consistent with thedeclined scope in net photosynthetic rates (Pn) and stomatal conductance (Gs), that is, P.armandi Franch.＞P. sylvestris L.var.mongolica Litv.＞P. tabulaeformis Carr＞P. bungeanaZucc.ex Endl., suggesting that the sensitivity to drought was related to genetic relation basedon UPGMA dendrogram of polymorphism site of proteins, and it is necessary to discuss thevariance in stress tolerance of these trees using proteomics method.Proteins responding to drought and high-temperature stress in P. armandi Franch., P.tabulaeformis Carr, P. bungeana Zucc.ex Endl., and P. sylvestris L.var.mongolica Litv. werestudied using proteomic methods. A total of 32 different proteins changed significantly wereobserved, and 15 proteins were identified using MALDI-TOF-MS. These proteins are quitediverse in their functions and are involved in photosynthesis, energy metabolism, osmoticregulation, protein processing and functioning as signal transduction. The data suggested thatthere have combined effects of responses to drought and high-temperature in P. armandiFranch. and P. sylvestris L.var.mongolica Litv. at the protein level, respectively, and alsosimilar molecular basis existed possibly between P. armandi Franch. and P. tabulaeformis Carr.The quantity of proteins, accounted for 43.8%, under drought and high-temperature in P.armandi Franch., was more than that of other three coniferous tree species, it suggested that P.armandi Franch. was more sensitive to these two kinds of stress, consistent with the resultobtained using the measurement of net photosynthetic rates and stomatal conductance.Based on the above studies, deep drought and high-temperature stress were imposed on P.armandi Franch.. When detected using proteomics methods, 22 of 27 different proteinschanged obviously were induced by high-temperature. It suggested again P. armandi Franch.was sensitive to high-temperature, in contrast with high-temperature.At the same time, P.×euramericana cv. '74/76', one of the important reforestationbroadleaved tree species in subtropical and temperate regions, was selected as a research modelusing the method mentioned above. Twenty-six proteins were found to change obviously inabundance under drought and high-temperature stress, and 12 similar proteins, larger thanconiferous tree species, were observed concurrently during these two kinds of stress. Itsuggested that the combined effect and similar molecular basis between drought andhigh-temperature were existed in P.×euramericana cv. '74/76'. The proteins participated inphotosynthesis account for 72%, which was higher than 16% in four coniferous tree species. Itsuggested that photosynthesis of P.×euramericana cv. '74/76' was influenced significantlyunder drought and high-temperature. In conclusion, based on our research results and previous research work, we found thephotosynthesis of investigated broadleaved tree was influenced significantly than that ofconiferous tree species during drought and high-temperature, and its drought tolerance wereweaker than other four coniferous tree species. Maybe, similar molecular basis and combinedeffect of drought and high-temperature in broadleaved and coniferous tree species were existedbecause many proteins with similar function were induced together. Expression of the majorityof proteins was increased, suggesting that all of these tree species taking an active part in theresponse to drought and high-temperature stress.