Physiological and Protein Responses to Drought in Four Pine Seedlings

Physiological and protein responses to drought stress in four pine seedlings, Pinus armandi Franch. (Pa), Pinus tabulaeformis Carr. (Pt), Pinus bungeana Zucc. ex Endl. (Pb) and Pinus sylvestris L. var. mongolica Litv. (Ps), were investigated using differential proteomics and water physiological indices. Firstly, the water physiological data showed that the decline rate of net photosynthesis rate, stomatal conductance, leaf water potential, turgor pressure except for under moderate drought stress was as follows: Pa > Ps > Pt > Pb. Pb and Pa always maintained the highest and lowest swelling pressure, respectively. Secondly, cluster analysis of 343 proteins indicated that the four pine species were classified into three groups with a genetic distance coefficient of 0.065. That is, five-needle-pine group (Pa), three-needle-pine group (Pb), two-needle-pine group (Pt and Ps), and the genetic distance between Pb and Pa was the farthest. The result was consistent with the declined rate in above physiological indices. Finally, for the differential proteomics analyzed, a total of 13 different proteins (P values < 0.01) changed significantly, the number of differentially expressed proteins was more in Pa (accounting for 46.2%) than the other three species, and 8 proteins were identified using matrix-assisted laser desorption/ionization time -of-flight mass spectrometry (MALDI-TOF-MS). These proteins are quite diverse in their functions and involved in photosynthesis, osmotic regulation and functioning as signal transduction. These results suggested that the sensitivities of the four pine species to drought were possibly related to genetic distance.