Autophagy‐related genes serve as heat shock protein 90 co‐chaperones in disease resistance against cassava bacterial blight

Abstract

SUMMARY Heat shock protein 90 (HSP90) is involved in plant growth and various stress responses via regulating protein homeostasis. Autophagy keeps cellular homeostasis by recycling the components of cellular cytoplasmic constituents. Although they have similar effects on cellular protein homeostasis, the direct association between HSP90 and autophagy signaling remains unclear in plants, especially in tropical crops. In this study, the correlation between HSP90 and autophagy signaling was systematically analyzed by protein–protein interaction in cassava, one of the most important economy fruit in tropic. In addition, their effects on plant disease response and underlying mechanisms in cassava were investigated by functional genomics and genetic phenotype assay. The potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex interacts with MeATGs and subsequently triggers autophagy signaling, conferring improved disease resistance to cassava bacterial blight (CBB). On the contrary, HSP90 inhibitor and autophagy inhibitor decreased disease resistance against CBB in cassava, and autophagy may be involved in the potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex‐mediated multiple immune responses. This study highlights the precise modulation of autophagy signaling by potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex in autophagy‐mediated disease resistance to CBB.

The coordination of melatonin and anti‐bacterial activity by EIL5 underlies ethylene‐induced disease resistance in cassava

“…In bread wheat, the ethylene‐responsive transcription factor ERF1 modulates pathogen‐triggered ROS accumulation and is involved in defense resistance to both the necrotrophic pathogen Rhizoctonia cerealis (Zhu et al., 2014) and the biotrophic pathogen powdery mildew (Liu et al., 2016). Here, ethylene and the ethylene‐responsive MeEIL5 increased flg22‐induced ROS burst to confer improved immunity, which was consistent with the results of other positive disease regulators (MeHSP90.9 and MeRAV5) in cassava (Wei et al., 2021b; Yan et al., 2021). In addition, overexpression of MeEIL5 or MeASMT2 or melatonin alleviated 1‐MCP‐mediated disease susceptibility and ROS burst, further indicating that MeEIL5 ‐integrated MeASMT2 transcript and melatonin accumulation underlie the ethylene‐improved immune response.…”

“…Recently, we revealed the essential role of melatonin biosynthesis in disease resistance to CBB in cassava (Wei et al, 2017). In addition, we also highlighted the crucial modulation of heat shock protein 90 (HSP90) in plant immunity through modulation of melatonin, SA, and auxin signaling and autophagy in cassava (Wei et al, 2021b;Wei et al, 2021a). However, the molecular pathways of immune responses in cassava remain elusive.…”

“…The assay to detect the bacterial flagellin peptide flg22‐induced ROS burst in cassava leaves has been described previously (Wei et al., 2021b; Zipfel et al., 2004). Briefly, cassava leaf discs were detached from 30‐day‐old seedlings via a puncher (diameter, 6 mm) and placed in sterile water overnight without light.…”

“…The bacterial pathogen Xam was cultivated and infiltrated as described in Wei et al (2021b) and Yan et al (2018). Briefly, Xam was cultivated on LB at 28°C overnight, transferred to liquid LB medium, and shaken at 28°C until the OD 600 of the Xam culture reached about 0.6.…”

Engineering bacterial blight-resistant plants through CRISPR/Cas9-targeted editing of theMeSWEET10apromoter in cassava

“…The bacterial growth assay showed that Xam11 populations in the four mutant lines were significantly smaller than that in the wild type at 3 dpi and 7 dpi (Figure 1I). Callose is deposited on the cassava cell wall during the early stages of Xam pathogen attack which restricts pathogen growth (Wei et al ., 2021). The leaves of the mutant cassava lines displayed significantly more callose depositions at 3 dpi than that in the wild type (Figure 1J).…”