Pseudomonas sp. TK35-L enhances tobacco root development and growth by inducing HRGPnt3 expression in plant lateral root formation

Rhizosphere colonization is a key requirement for the application of plant growth-promoting rhizobacteria (PGPR) as a biofertilizer. Signaling molecules are often exchanged between PGPR and plants, and genes in plants may respond to the action of PGPR. Here, the luciferase tuxAB gene was electrotransformed into Pseudomonas sp. strain TK35, a PGPR with an affinity for tobacco, and the labelled TK35 (TK35-L) was used to monitor colonization dynamics in the tobacco rhizosphere and evaluate the effects of colonization on tobacco growth and root development. The transcript levels of the hydroxyproline-rich glycoprotein HRGPnt3 gene, a lateral root induction indicator, in tobacco roots were examined by qPCR. The results showed that TK35-L could survive for long periods in the tobacco rhizosphere and colonize new spaces in the tobacco rhizosphere following tobacco root extension, exhibiting significant increases in root development, seedling growth and potassium accumulation in tobacco plants. The upregulation of HRGPnt3 transcription in the inoculated tobacco suggested that TK35-L can promote tobacco root development by upregulating the transcript levels of the HRGPnt3 gene, which promotes tobacco seedling growth. These findings lay a foundation for future studies on the molecular mechanism underlying the plant growth-promoting activities of PGPR. Furthermore, this work provided an ideal potential strain for biofertilizer production.