Differential partitioning of seed-inhabiting methylotrophs in the endosphere of wheat plants

Both endophytes, microorganisms that reside within plants, and methylotrophs, which grow using methanol produced from plant leaves, play key roles in protecting plants against biotic and abiotic stresses. However, the source of endophytes and the mechanisms of their selection in plants are poorly understood. Therefore, experiments were carried out to identify wheat seed methylotrophic endophytes and evaluate their partitioning in root, stem and leaf of aseptic-controlled plants cultivated from surface-sterilized seeds.

The counts of endophytic methanol utilizers were higher in leaf tissue than in stem, root and seed, as estimated using viable counts and qPCR targeting rrn gene. The methanol dehydrogenase subunit mxaF gene was PCR-detected in all pink-coloured isolates that grew using methanol or succinate. These pink-pigmented facultative methylotrophs (PPFM) were dominant in shoot tissue. Using mass spectrometry for alkaloid content analysis, peganine was detected as a peak 16.6% higher in root than shoot. Root extracts and peganine alone inhibited the growth of PPFM.

PPFM transmitted from seed are more abundant in shoot than root. How plant compounds such as peganine are involved in the methylotrophic endo-phytomicrobiome dynamics remains to be better characterized.