Characterization of a small cryptic plasmid from endophytic Pantoea agglomerans and its use in the construction of an expression vector

Abstract

A circular cryptic plasmid named pPAGA (2,734 bp) was isolated from Pantoea agglomerans strain EGE6 (an endophytic bacterial isolate from eucalyptus). Sequence analysis revealed that the plasmid has a G+C content of 51% and contains four potential ORFs, 238(A), 250(B), 131(C), and 129(D) amino acids in length without homology to known proteins. The shuttle vector pLGM1 was constructed by combining the pPAGA plasmid with pGFPmut3.0 (which harbors a gene encoding green fluorescent protein, GFP), and the resulting construct was used to over-express GFP in E. coli and P. agglomerans cells. GFP production was used to monitor the colonization of strain EGE6gfp in various plant tissues by fluorescence microscopy. Analysis of EGE6gfp colonization showed that 14 days after inoculation, the strain occupied the inner tissue of Eucalyptus grandis roots, preferentially colonizing the xylem vessels of the host plants.

Seed Endophyte Microbiome of Crotalaria pumila Unpeeled: Identification of Plant-Beneficial Methylobacteria

“…To the best of our knowledge, the present study is the first in which a seed endophyte was observed colonising the stem xylem vessels in the presence of metal stress as environmental variable ( Figure 5 and Figure 6 ), suggesting that the exposure of the host plant to metals promotes the migration of specific endophytes to the aboveground plant parts. In several other studies, bacterial strains isolated from the rhizosphere [ 47 , 48 ], and some endophytes from stems [ 49 , 50 , 51 ] and seeds [ 52 , 53 , 54 ] were shown to colonise the internal root and shoot tissues (including cortex and xylem) under control conditions. Using gfp-tools and under metal exposure conditions, Zhang et al [ 55 ] reported that labelled root endophytes of Sedum alfredii ( Burkholderia and Variovorax ) were observed inside the root cortex, but no colonisation of plant vascular system was reported.…”