Exogenously Applied Spermidine Alleviates Hypoxia Stress in Phyllostachys Praecox Seedlings Via Changes in Endogenous Hormones and Gene Expression

Abstract PurposeHypoxia stress is thought to be one of the major abiotic stresses that inhibits the growth and development of higher plants. Phyllostachys pracecox is sensitive to oxygen and suffers soil hypoxia during cultivation; however, the corresponding measures to mitigate this stress are still limited in practice. In this study, a simulated hypoxia stress with flooding was conducted to investigate the regulatory effect of Spermidine (Spd) on P. praecox seedlings. MethodsIndicators including growth, membrane lipid peroxidation, S-adenosylmethionine decarboxylase (SAMDC), ACC oxidase (ACO) and ACC synthetase (ACS) activities, indole-3-acetic acid (IAA) and abscisic acid (ABA) content, and expression of hormone-related genes in P. praecox were measured. ResultsApplication of 1 mM and 2 mM Spd could alleviate plant growth inhibition and reduce oxidative damage from hypoxia stress. Exogenous Spd significantly (P<0.05) increased SAMDC activity, enhanced ABA and IAA content, and reduced ACO and ACS activities to protect membranes from lipid peroxidation. Moreover, exogenous Spd up-regulated the expression of auxin-related genes auxin responsive factor1 (ARF1), auxin1 protein (AUX1), auxin2 protein (AUX2), auxin3 protein (AUX3) and auxin4 protein (AUX4), and down-regulated the expression of ethylene-related ACO and ACS genes during flooding. ConclusionThe results indicated that exogenous Spd altered hormone concentrations and the expression of hormone-related genes, thereby protecting the bamboo growth. Our data suggest that Spd can be used to reduce hypoxia-induced cell damage and improve the adaptability of P. praecox to flooding stress.