Summary: C‐type lectins (CTLs), a class of multifunctional proteins, are numerous in nematodes. One CTL gene, Mg01965 , shown to be expressed in the subventral glands, especially in the second‐stage juveniles of the root‐knot nematode Meloidogyne graminicola , was further analysed in this study. In vitro RNA interference targeting Mg01965 in the preparasitic juveniles significantly reduced their ability to infect host plant roots. Immunolocalizations showed that Mg01965 is secreted by M. graminicola into the roots during the early parasitic stages and accumulates in the apoplast. Transient expression of Mg01965 in Nicotiana benthamiana and targeting it to the apoplast suppressed the burst of reactive oxygen species triggered by flg22. The CTL Mg01965 suppresses plant innate immunity in the host apoplast, promoting nematode parasitism in the early infection stages.

Chitinases are enzymes that catalyze the degradation of chitin, a major component of the cell walls of pathogenic fungi and cuticles of insects, gaining increasing attention for the control of fungal pathogens and insect pests. Production of recombinant chitinase in a suitable host can result in a more pure product with less processing time and a significantly larger yield than that produced by native microorganisms. The present study aimed to express the synthetic chi42 gene (syncodChi42), which was optimized from the chi42 gene of Trichoderma asperellum SH16, in Escherichia coli to produce 42 kDa chitinase (Ta-CHI42); then determined the activity of this enzyme, characterizations and in vitro antifungal activity as well as its immunogenicity in mice. The results showed that Ta-CHI42 was overexpressed in E. coli. Analysis of the colloidal chitin hydrolytic activity of purified Ta-CHI42 on an agar plate revealed that this enzyme was in a highly active form. This is a neutral chitinase with pH stability in a range of 6–8 and has an optimum temperature of 45°C with thermal stability in a range of 25–35°C. The chitinolytic activity of Ta-CHI42 was almost completely abolished by 5 mM Zn²⁺ or 1% SDS, whereas it remained about haft under the effect of 1 M urea, 1% Triton X-100 or 5 mM Cu²⁺. Except for ions such as Mn²⁺ and Ca²⁺ at 5 mM that have enhanced chitinolytic activity; 5 mM of Na⁺, Fe²⁺ or Mg²⁺ ions or 1 mM EDTA negatively impacted the enzyme. Ta-CHI42 at 60 U/mL concentration strongly inhibited the growth of the pathogenic fungus Aspergillus niger. Analysis of western blot indicated that the polyclonal antibody against Ta-CHI42 was greatly produced in mice. It can be used to analyze the expression of the syncodChi42 gene in transgenic plants, through immunoblotting assays, for resistance to pathogenic fungi.