Physiological And Proteomic Analysis Of Populus Simonii × P.nigra Roots In Response To NaCl

Salinity is one of the major threatens that affect agricultural production and ecological environment.Populus simonii × P.nigra,which is the hybrid of P.simonii and P.nigra,has mild salt tolerant ability.It is widely applied in greening and afforestation.Plant roots are the primary sites for sensing salt signals.It is important to investigate the salt-responsive mechanism within Populus simonii × P.nigra roots.In this study,we use Populus simonii x P.nigra roots as materials to investigate the NaCl-responsive molecular mechanisms through morphology,physiological and proteomics approaches.We found that the membrane permeability was destroyed,osmoprotectants(proline,betaine and soluble sugar)accumulated,and the antioxidant enzyme activity increased by NaCl stress in roots of Populus simonii x P.nigra.Meanwhile,quantitative proteomics analysis identified 75 NaCl-responsive proteins in Populus simonii x P.nigra roots,most of which were involved in signal transduction,stress and defense,membrane and transport,carbohydrate and energy metabolism,as well as protein synthesis,processing and degradation.Physiological and proteomic results revealed the specific NaCl-responsive strategies existed in Populus simonii × P.nigra roots.The main strategies include:(1)Morphology and relative water content results indicated the growth of roots was suppressed under NaCl stress,and inhibition is more obvious with the increase of stress intensity.(2)Superoxide dismutase,catalase,ascorbate glutathione cycle,glutathione peroxidase/glutathione S-transferase and peroxidase pathway were activated to scavenge reactive oxygen species,which could reduce the oxidative damages caused by salt stress.(3)A large number of osmoprotectants such as proline,betaine and soluble sugar were accumulated in varying degrees to maintain the osmotic balance inside and outside cells.(4)V-type proton ATPase subunit B2 abundance decreased in 150 mM NaCl stress drop,which inhibited the Na+efflux to a certain extent.(5)E3 ubiquitin-protein ligase UPL4 and proteasome subunit alpha type-3 in ubiquitin/26S proteasome degradation pathway were decreased by 150 mM NaCl stress.It indicated protein degradation was inhibited in 150 mM NaCl stress.This provides more important imformation for further underlying the stress response and metabolic regulative mechanisms in Populus simonii x P.nigra roots.