Necessity of rice resistance to planthoppers for OsEXO70H3 regulating SAMSL excretion and lignin deposition in cell walls

Abstract

Summary The planthopper resistance gene Bph6 encodes a protein that interacts with OsEXO70E1. EXO70 forms a family of paralogues in rice. We hypothesized that the EXO70‐dependent trafficking pathway affects the excretion of resistance‐related proteins, thus impacting plant resistance to planthoppers. Here, we further explored the function of EXO70 members in rice resistance against planthoppers. We used the yeast two‐hybrid and co‐immunoprecipitation assays to identify proteins that play roles in Bph6‐mediated planthopper resistance. The functions of the identified proteins were characterized via gene transformation, plant resistance evaluation, insect performance, cell excretion observation and cell wall component analyses. We discovered that another EXO70 member, OsEXO70H3, interacted with BPH6 and functioned in cell excretion and in Bph6‐mediated planthopper resistance. We further found that OsEXO70H3 interacted with an S‐adenosylmethionine synthetase‐like protein (SAMSL) and increased the delivery of SAMSL outside the cells. The functional impairment of OsEXO70H3 and SAMSL reduced the lignin content and the planthopper resistance level of rice plants. Our results suggest that OsEXO70H3 may recruit SAMSL and help its excretion to the apoplast where it may be involved in lignin deposition in cell walls, thus contributing to rice resistance to planthoppers.

Exocyst functions in plants: secretion and autophagy

“…The exocyst subunits subfamily EXO70.2 and EXO70.3 members EXO70H and EXO70I function in the establishment of a symbiotic relationships with rhizobia or mycorrhiza as shown in legumes [91][92][93]. Exocyst also participates in resistance to animal pests such as nematodes or planthoppers [94,95].…”

Large scale rice germplasm screening for identification of novel brown planthopper resistance sources

“…49, 3.50-5.49, or 5.50-9.00 were designated as resistant (R), moderately resistant (MR), or susceptible (S) to BPH, respectively(Heinrichs et al 1985;Wu et al 2022). As shown in Supplementary TableS2, 176 accessions (31.4%) were resistant to the Bangladesh type with the rating scores between 0 and 3.49, 138 accessions (24.6%) exhibited moderate resistance with scores ranging from 3.50 to 5.49, and a total of 246 accessions (43.9%) were susceptible to the Bangladesh type with scores between 5.50 and 9.00.…”

Lignin, glutathione and kinases play important roles inPaspalum regnelliidefense against spittlebug (Mahanarva spectabilis) attack

“…Among the cell wall components that can cause mechanical difficulties in infestation is lignin, which reduces the palatability of plants for herbivores (Xiao et al ., 2023). It increases cellular rigidity, and its higher concentration has already been described as a resistance factor (Lynch et al ., 2021; Wu et al ., 2022), avoiding colonization of the plant by insects, which characterizes the antixenosis resistance mechanism (Kogan and Ortman, 1978). In our root histochemical analyses, it was possible to observe that lignification occurs only in the walls of the resistant genotype, confirming that there is already a natural anatomical predisposition that makes it difficult to choose these plants as hosts.…”

“…These defenses start with physical barriers, including cell wall adaptations, to avoid colonization for feeding (Zhang et al, 2020b). Lignin, for instance, serves as a mechanical component that reduces plant palatability for herbivores (Xiao et al, 2023), increases cellular rigidity, and prevents insect colonization (Lynch et al, 2021; Wu et al, 2022), thereby conferring resistance to antixenosis (Kogan and Ortman, 1978).…”