C-type lectins (CTLs) are a superfamily of Ca²⁺-dependent carbohydrate-recognition proteins, and an important pattern recognition receptor (PRR) in insect innate immunity which can mediate humoral and cellular immunity in insects.  In this study, we report a novel dual carbohydrate-recognition domain (CRD) CTL from Plutella xylostella which we designate PxIML.  PxIML is a protein with a 969 bp open reading frame (ORF) encoding 322 amino acids, containing a signal peptide and a dual-CRD with EPN (Glu₁₂₄-Pro₁₂₅-Asn₁₂₆) and QPD (Gln₂₇₄-Pro₂₇₅-Asp₂₇₆) motifs.  The expression of PxIML mRNA in the fat body was significantly higher than in hemocytes and midgut.  The relative expression levels of PxIML in the whole insect and the fat body were significantly inhibited after infection with Bacillus thuringiensis 8010 (Bt8010) at 18 h, while they were significantly upregulated after infection with Serratia marcescens IAE6 or Pichia pastoris.  The recombinant PxIML (rPxIML) protein could bind to the tested pathogen-associated molecular patterns (PAMPs), and the bacteria of Enterobacter sp. IAE5, S. marcescens IAE6, Staphylococcus aureus, Escherichia coli BL21, and Bt8010 in a Ca²⁺-dependent manner, however, it showed limited binding to the fungus, P. pastoris.  The rPxIML exhibited strong activity in the presence of Ca²⁺ to agglutinate Bt8010, Enterobacter sp. IAE5 and S. aureus, but it only weakly agglutinated with E. coli BL21, and could not agglutinate with S. marcescens IAE6 or P. pastoris.  Furthermore, the rPxIML could bind to hemocytes, promote the adsorption of hemocytes to beads, and enhance the phenoloxidase (PO) activity and melanization of P. xylostella.  Our results suggest that PxIML plays an important role in pathogen recognition and in mediating subsequent humoral and cellular immunity of P. xylostella.

The fungistatic activity of a lactic acid bacterium, which had been isolated from yellow pitahaya cultures, against fungi associated with basal rot (Fusarium oxysporum and Fusarium fujikuroi) was measured in the present study.  Its activity was assessed in three fractions: fermented (S1), metabolic products (S2), and biomass (S3), using two fermentation substrates: Man Rogosa Sharpe agar (MRS) and potato dextrose agar (PDA).  The bacterium was molecularly identified as Lactobacillus plantarum.  S3 reduced F. fujikuroi growth by 100% over 48 h of fermentation, which occurred during the stationary phase of bacterial growth.  The three fractions’ fungistatic activity against F. fujikuroi depended on the substrate employed.  The fermentation kinetic parameters for L. plantarum indicated that its specific growth rate was 0.46 h^–1, with 93.63% substrate consumption, 0.045 kg kg^–1 cell yield, and 0.54 kg kg^–1 product yield.  The kinetic parameters calculated will allow for bacteria production scaling.  These in-vitro trials reveal L. plantarum’s possible application as a biocontrol agent for diseases associated with Fusarium.  However, further ex-vivo and in-vivo researches are required to demonstrate its behavior in crops. 

 

Avocado is one of the most important crops in the world, and Mexico is the largest producer of this fruit.  Several insect pests affect its production, and thrips are amongst the most important.  A key step in the design of control methods is accurate species identification.  Despite this, formal reports on species diversity of thrips in Mexico are very scarce.  Morphological identification can sometimes be time-consuming and inconclusive.  Therefore, we explored the species diversity of thrips in Mexican avocado orchards (Michoacan state) based on partial sequences of the mitochondrial gene cytochrome oxidase subunit I (COI).  Forty-four specimens were analysed, which represented approximately 8% of all individuals collected from five localities distributed in three Municipalities.  All specimens were analysed using the COI marker, and specimens within the genera Frankliniella were also analysed using a marker within the D2 domain of the 28S (28SD2) nuclear ribosomal DNA.  Molecular identifications were confirmed using morphological taxonomy.  Overall, six genera were found (Neohydatothrips, Scirtothrips, Frankliniella, Arorathrips, Caliothrips and Leptothrips).  All genera contained only one species, except Frankliniella, for which there were six species.  Data from the two molecular markers suggest the existence of cryptic species within Mexican F. occidentalis populations.