Genome-wide identification of key genes responding to salt stress in Populus alba

Abstract

Background The molecular mechanism of forest trees responding to salt stress remains poorly understood. As a fast-growing and widely adapted tree species, Populus alba is planted in the world. Understanding the molecular mechanism of P. alba responding to salt stress is helpful to improve the yield of P. alba artificial forest in salinized land. Results This study investigated the phenotypic and physiological characteristics of P. alba seedlings under 300 mM NaCl stress. After seven days of salt stress, the leaves of P. alba turned yellow and fell off. Whether under normal growth conditions or salt stress, CAT activities in roots were significantly higher than that in leaves. The root viability of P. alba decreased significantly within 2 h of salt treatment, but gradually increased after 2 h of salt treatment. Intercellular CO₂ concentration of leaves of P. alba increased significantly after 72 h of salt treatment, while other photosynthetic parameters decreased significantly after 72 h of salt stress. Chlorophyll a and chlorophyll b in leaves of P. alba decreased gradually after 9 h of salt stress. The ratio of Na⁺/K⁺ in roots and leaves of P. alba gradually increased after 1 and 2 h of salt stress, respectively. ABA and cytokinin contents in roots and leaves of P. alba under salt stress were increased significantly. Time-series transcriptomes of roots, stems, leaves, and apical buds of P. alba under NaCl stress were analyzed. Based on gene expression, physiological and biochemical data in P. alba under salt stress, we performed weighted gene co-expression network analysis. Thirty-two candidate key genes of P. alba responding to salt stress were identified. Twenty-four candidate key genes showed salt tolerance in Saccharomyces cerevisiae. Especially for the four genes (Poalb01G005590, Poalb16G007310, Poalb01G036340, and Poalb06G010440), each exhibited strong tolerance to different kinds of salt stress. Conclusion The results of this study provide a new insight into the molecular mechanism of trees responding to salt stress.