Genome mining of Photorhabdus luminescens TNAU1 reveals novel gene assets with insecticidal and nematicidal properties

Abstract

Photorhabdus luminescens is an enterobacterium, a symbiont of beneficial nematodes with broad-spectrum insecticidal potential against various important pests of crops. Nowadays these bacteria are largely exploited to decipher their antagonistic nature against plant parasitic nematodes and insects. The complete genome analysis confirmed the isolate TNAU1 as P. luminescens with a circular genome of 5,247,491 bp (5.2 Mb) length and 42.57 % GC content. The genome annotation revealed the presence of 5221 coding sequences (CDS) genes, 68 transfer RNA (tRNA) genes, and 3 ribosomal RNA (rRNA) genes. Nonribosomal peptide synthetase (NRPS) gene clusters in the genome of TNAU1 included Minimycin, Kolossin, luminmycin A, prepiscibactin, xenocoumacin 1, mevalagmapeptide A, Xenematide, Tolassin, luminmide B, putrebactin and Ririwpeptode B. Moreover, genome assemblies also exhibited the presence of 10 homologs corresponding to nematode virulence and 15 homologs of insect-virulent proteases. These proteins make P. luminescens a promising model for studying symbiosis and host-pathogen interactions through removing competitors, host colonization, invasion, and bioconversion of the insect cadaver. To identify its antagonistic ability against nematodes and insect pests, P. luminescens TNAU1 was evaluated against root-knot nematode, Meloidogyne incognita, and fall armyworm, Spodoptera frugiperda. The results exhibited that P. luminescens inhibited the egg hatching (98.92 %) and mortality of juveniles (94.19 %) of M. incognita over control under in vitro conditions and similarly, 78.3 % insect mortality was observed with LC50 of 684.2 ppm against S. frugiperda. The current study emphasizes the importance of exploiting the P. luminescens to manage important pests and nematodes in crops.