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 .