BxCDP1 from the pine wood nematode Bursaphelenchus xylophilus is recognized as a novel molecular pattern.

The migratory plant-parasitic nematode Bursaphelenchus xylophilus is the causal agent of pine wilt disease, which causes serious damage to pine forests in China. Plant immunity plays an important role in plant resistance to multiple pathogens. Activation of the plant immune system is generally determined by immune receptors, including plant pattern recognition receptors, which mediate pattern recognition. However, little is known about molecular pattern recognition in the interaction between pines and B. xylophilus. Based on the B. xylophilus transcriptome at the early stages of infection and Agrobacterium tumefaciens-mediated transient expression and infiltration of recombinant proteins produced by Pichia pastoris in many plant species, a novel molecular pattern (BxCDP1) was characterized in B. xylophilus. We found that BxCDP1 was highly up-regulated at the early infection stages of B. xylophilus, and was similar to a protein in Pararhizobium haloflavum. BxCDP1 triggered cell death in Nicotiana benthamiana when secreted into the apoplast, and this effect was dependent on brassinosteroid-insensitive 1-associated kinase 1, but independent of suppressor of BIR1-1. BxCDP1 also exhibited cell death-inducing activity in pine, Arabidopsis, tomato, pepper, and lettuce. BxCDP1 triggered reactive oxygen species production and the expression of PAMP-triggered immunity marker genes (NbAcre31, NbPTI5, and NbCyp71D20) in N. benthamiana. It also induced the expression of pathogenesis-related genes (PtPR-3, PtPR-4, and PtPR-5) in Pinus thunbergii. These results suggest that as a new B. xylophilus molecular pattern, BxCDP1 can not only be recognized by many plant species, but also triggers innate immunity in N. benthamiana and defence responses of P. thunbergii.

An Effector, BxSapB1, Induces Cell Death and Contributes to Virulence in the Pine Wood Nematode Bursaphelenchus xylophilus.

The pine wood nematode (PWN) Bursaphelenchus xylophilus has caused serious damage to pine forests in China. Effectors secreted by phytonematodes play a role in host infection. We identified and characterized an effector, BxSapB1, based on the B. xylophilus transcriptome at the early stages of infection and the transient expression of proteins in Nicotiana benthamiana. BxSapB1 triggered cell death in N. benthamiana when secreted into the apoplast, and this effect was independent of N. benthamiana brassinosteroid-insensitive 1-associated kinase 1 (NbBAK1) and suppressor of BIR1-1 (NbSOBIR1). The signal peptide of BxSapB1 was proven to be functional in yeast using the yeast signal sequence trap system and BxSapB1 was strongly expressed in the subventral gland cells of B. xylophilus, as revealed by in-situ hybridization. In addition, based on local BLAST analysis, the BxSapB1 showed 100% identity to BUX.s00139.62, which was identified from the B. xylophilus secretome during Pinus thunbergii infection. BxSapB1 was upregulated in a highly virulent strain and downregulated in a weakly virulent strain of PWN at the early stages of infection. RNA interference assays showed that silencing BxSapB1 resulted in decreased expression of pathogenesis-related genes (PtPR-1b, PtPR-3, and PtPR-5) as well as delayed onset of symptoms in P. thunbergii infected by B. xylophilus. The combined data suggest that BxSapB1 can trigger cell death in N. benthamiana and that it contributes to the virulence in B. xylophilus during parasitic interaction.

Synthesis of 1-Thio-Substituted Isoquinoline Derivatives by Tandem Cyclization of Isothiocyanates.

A copper-catalyzed tandem arylation-cyclization process to access 1-(arylthio)isoquinolines from isothiocyanates and diaryliodonium salts is described. It is the first general method to construct the potentially useful 1-(arylthio)isoquinoline derivatives. Moreover, 1-(methylthio)isoquinoline derivatives were also achieved successfully with MeOTf instead of diaryliodonium salts under metal-free conditions. Mechanistic studies reveal that these two processes proceed in different routes. This method has been successfully applied to the synthesis of quinazolinone alkaloid rutaecarpine.

Microarray profiling reveals microRNAs involving soybean resistance to Phytophthora sojae.

MicroRNAs (miRNAs), a group of small noncoding RNAs, may serve as a class of post-transcriptional regulators in plant immune systems. Nevertheless, little is known about their roles in plant immune response to the oomycete pathogens. To identify miRNAs involved in the response of soybean to Phytophthora sojae, we examined expressional patterns of miRNAs upon infection by P. sojae by microarray analysis in three soybean cultivars: Williams (susceptible), Conrad (quantitative resistance), and Williams 82 (qualitative resistance). Expression of a number of miRNAs was significantly altered upon infection and (or) in the different genotypes. qRT-PCR data with some miRNAs further confirmed the microarray results. Comparative analysis of the selected miRNAs and their targeted gene expression datasets uncovered many reciprocally expressed miRNA-target pairs, which could proposed a feedback circuit between miRNA(s) and protein-coding genes. These results may serve as a basis for further in-depth studies of miRNAs involved in soybean resistance to P. sojae.