Expression of Castanea crenata Allene Oxide Synthase in Arabidopsis Improves the Defense to Phytophthora cinnamomi

Abstract

Allene oxide synthase (AOS) is a key enzyme of the jasmonic acid (JA) signaling pathway. The AOS gene was previously found to be upregulated in an Asian chestnut species resistant to infection by the oomycete Phytophthora cinnamomi (Castanea crenata), while lower expression values were detected in the susceptible European chestnut (Castanea sativa). Here, we report a genetic and functional characterization of the C. crenata AOS (CcAOS) upon its heterologous gene expression in a susceptible ecotype of Arabidopsis thaliana, which contains a single AOS gene. It was found that Arabidopsis plants expressing CcAOS delay pathogen progression and exhibit more vigorous growth in its presence. They also show upregulation of jasmonic acid and salicylic acid-related genes. As in its native species, heterologous CcAOS localized to plastids, as revealed by confocal imaging of the CcAOS-eGFP fusion protein in transgenic Arabidopsis roots. This observation was confirmed upon transient expression in Nicotiana benthamiana leaf epidermal cells. To further confirm a specific role of CcAOS in the defense mechanism against the pathogen, we performed crosses between transgenic CcAOS plants and an infertile Arabidopsis AOS knockout mutant line. It was found that plants expressing CcAOS exhibit normal growth, remain infertile but are significantly more tolerant to the pathogen than wild type plants. Together, our results indicate that CcAOS is an important player in plant defense responses against oomycete infection and that its expression in susceptible varieties may be a valuable tool to mitigate biotic stress responses.

The Bradyrhizobium diazoefficiens type III effector NopE modulates the regulation of plant hormones towards nodulation in Vigna radiata

“…CHS expression leads to the accumulation of flavonoid and isoflavonoid phytoalexins and is involved in the salicylic acid (SA) defence pathway 10 . We also found decreased levels of pathogen-inducible SA ( SGT1 ), thaumatin-like protein 1 and defensin, which are known to be involved in plant immune responses against pathogenic invasion 11 , 12 . The homologue of the auxin efflux carrier compartment ( PIN1 ) gene 13 was also downregulated in response to USDA110 inoculation.…”

“…6 ). Defensins are known to be involved in plant immunity responses of the jasmonic acid (JA) pathway 12 . We propose a model modulated by USDA110 NopE in Fig.…”

European and American chestnuts: An overview of the main threats and control efforts

“…The gene Allene oxide synthase ( CcAOS ), an ortholog of a key enzyme of the JA pathway, was also selected from 2015 transcriptomes ( Serrazina et al, 2015 ). The importance of this gene in plant defense responses against PC was demonstrated after being overexpressed in a susceptible Arabidopsis ecotype (Ler-0), resulting in a delay of infection progression and an increase in tolerance ( Table 2 ; Serrazina et al, 2021 ).…”

Warming Scenarios and Phytophthora cinnamomi Infection in Chestnut (Castanea sativa Mill.)

“…Phytophthora cinnamomi ( Pc ) is a soil-borne pathogen (Stramenopila, Oomycota) that infects almost 5000 plant species, including many that are significant in agriculture, forestry and horticulture [ 30 ]. Recent studies on chestnut have addressed the genetic background, adaptation, maternal effects, regeneration and histology of trees in response to Pc infection [ 35 , 36 , 37 , 38 , 39 , 40 ] and elucidated the metabolic, proteomic and hormonal changes in chestnut [ 10 , 41 , 42 ]. The impact of ink disease on chestnut depends on the environment, and is more severe in areas with high temperature, low relative humidity and dry summers [ 43 ].…”