Working group session:
Functional Genomics
Presentation type:
poster
Authors:
Mo, Huijuan; Wang, Xingfen; Zhang, Yan ; Zhang, Guiyin ; Ma, Zhiying
Presenter:
Mo, Huijuan
Correspondent:
Ma, Zhiying
Abstract:
Verticillium dahliae is a destructive, soil-borne fungal pathogen that causes vascular wilt disease in many economically important crops worldwide. Polyamine (PA) is ubiquitous aliphatic amine that has been implicated in various physiological and developmental processes in all living organisms. Plant polyamine oxidase (PAO) involved in the terminal catabolism of PA has been previously hypothesized down-regulating of PA level with enhanced plant defense against various pathogens. However, the effect of engineering PAO in host plants is rarely known on the hemibiotrophic fungal pathogen V. dahliae, and the underlying mechanism of PA on defense response in plants is poorly understood. Here, a novel polyamine oxidase (GhPAO) was identified by screening SSH library of G. hirsutum cv. ‘Jimian 20’ and the cDNA library of G. barbadense cv. ‘Pima 90-53’. Its expression was rapidly induced in the resistant ‘Jimian 20’ and suppressed in the susceptible ‘Han 208’ after V. dahliae inoculation. Overexpression of GhPAO in Arabidopsis thaliana exhibited improved resistance to V. dahliae, and unexpectedly elevated all of three PA, putrescine, spermidine and Spm, by driving ten genes accounting for PA biosynthesis (AtADC1/2, AtSAMDC, AtSPDS1/2, AtSPMS and AtPAO1/2/3/4/5) after V. dahliae infection with real-time RT-PCR analysis. The level of hydrogen peroxide (H2O2), as the product of PAO-derived PA oxidation and the signaling component, was elevated pre- and post-inoculation in GhPAO overexpression lines when compared to the wild type with ELISA analysis. The hormone salicylic acid and phytoalexin camalexin were distinctly increased in GhPAO overexpression lines after V. dahliae inoculation when compared to the wild type by HPLC experiment. PA and H2O2 showed efficient inhibition to V. dahliae conidial proliferation and hyphal growth via dual culture technique in vitro, and Spm exhibited the highest antifungal activity. Moreover, Spm and H2O2 could promote phytoalexin camalexin biosynthesis via inducing three pathogen-responsive mitogen-activated protein kinases (MPKK1, MPK3 and MPK6) and two downstream Cytochrome P450 proteins (CYP71A13 and PAD3), with exogenous application of Spm and H2O2 in the wild type pre-inoculation. In addition, quantification of free PA by HPLC in cotton showed that all of three PA were gradually decreased in two susceptible upland cotton, ‘Han 208’ and ‘CCRI 8’, after V. dahliae inoculation, while showed increase in two resistant sea island cotton, ‘Pima 90-53’ and ‘Hai 7124’. In all, GhPAO, a novel PAO from cotton, contributes to plant resistance against the hemibiotrophic fungal pathogen V. dahliae via elevating secondary antimicrobial compounds, PA, H2O2 and phytoalexin camalexin, and plant hormone salicylic acid levels.