ArPAOs from A. roxburghii showed essential roles in polyamine mediating water stress tolerance

Abstract

Anoectochilus roxburghii is a precious Chinese herb with excellent pharmacological effects. When meet stress, plants produced polyamines (PAs) which are identified in active tissues and play crucial roles in stress responses. Nevertheless, the molecular mechanism of PAs responding to stress in A. roxburghii were largely unknown. Here, for the first time, three PAOs in A. roxburghii were identified from transcriptome data and functionally analyzed. Expression analysis was performed using fluorescence quantitative PCR and eventually, transgenic Arabidopsis thaliana were created to confirm the biological function of ArPAOs. It was found that the highest expression was in young flower buds and the expression levels of three ArPAO genes in various tissues were also different, which indicated their different catalytic preferences and functions. Under the treatment of exogenous spermine and spermidine, the expression of three ArPAOs fluctuated and the overall expression level increased. Overexpression (OE) of ArPAOs could enhance water stress tolerance through mediating polyamine catabolism. It might because the excessive expression of ArPAOs reduce the content of spermine and spermidine, creating a negative feedback regulation upstream and causes plants manufacturing PAs which reinforce water stress tolerance. Taken together, the study firstly reported the overexpression of ArPAOs enhance plant water stress tolerance and regulate the content of polyamines. This work will provide a vital theoretical foundation for uncovering the operation and regulatory mechanism of ArPAOs in promoting plant development and managing stress.