Molecular characterization and functional analysis of akt-1 in pinewood nematode, Bursaphelenchus xylophilus

Bursaphelenchus xylophilus is the causal agent of pine wilt disease, which leads to the devastation of millions of hectares of pine trees worldwide. Protein kinase B (AKT) is a structurally conserved serine/threonine kinase with a pleckstrin homology domain and a kinase domain, and it plays versatile biological roles across different animal kingdoms. We, therefore, investigated the molecular characteristics and biological function of akt-1 in B. xylophilus (Bxy-akt-1). In propagative stages, reverse transcription quantitative real-time PCR revealed that Bxy-akt-1 expression gradually increased during embryogenesis, reaching the highest level at the second-stage juvenile (J2), and then steadily decreased from J3 to adults. Intriguingly, the expression of Bxy-akt-1 was significantly higher in males than in females. Moreover, the expression level of Bxy-akt-1 in dispersal third-stage dauer larvae (DL3) was higher than that in J2, but it decreased to normal level in DL4. Bxy-akt-1 promoter::gfp reporter constructed in Caenorhabditis elegans was utilized to mimic the spatio-temporal expression pattern of Bxy-akt-1. The results showed that Bxy-akt-1 was broadly expressed in the hypodermis around the head during embryogenesis and was mainly expressed in the muscle cells of pharynx, vulva, tail and nerve systems in post-embryonic stages. Abnormal embryos were observed, and the hatching rate was significantly decreased after Bxy-akt-1 was knocked down in B. xylophilus, but no constitutive developmental arrest of dauer larvae was observed. The results indicated that Bxy-akt-1 is indispensable for embryogenesis, but might not play a significant role in controlling dauer entry, as in C. elegans.

Automated summary

The study revealed that Bxy-akt-1 in Bursaphelenchus xylophilus shows stable expression changes during embryogenesis, with significantly higher expression in males and increased levels in dispersal third-stage dauer larvae. It is widely expressed in the organism and plays a crucial role in embryogenesis, while potentially not being a key factor in controlling the entry into the dormant stage.