Background: Endophytic bacteria release active metabolites by utilizing nutrients secreted by plants
and induce gene expression and enhance plant growth under abiotic stresses.
Objective: To understand the dynamics of drought markers (27 genes) in endophyte Acinetobacter sp.
associated maize under drought compared to control plants using quantitative real-time PCR (qRTPCR).
Method and Result: Four endophytic bacteria Pseudomonas putida FMZR9, Acinetobacter baumannii
MZ30V92, Enterobacter asburiae MRC12, and Sinorhizobium meliloti MRC31 screened for stress tolerance
showed 1- aminocyclopropane-1-carboxylic acid (ACC)-deaminase activity, exopolysaccharides
(EPS), sugars, amino acids and proline under no-stress and stressed conditions [-1.02 matric potential
(MPa)]. Endophytes showed protease, pectinase, cellulase and chitinases as well as swimming,
swarming (except FMZR9) and twitching motility (except FMZR9 and MRC31). Acinetobacter baumannii
MZ30V92 transformed with gfp gene colonized inside epidermal and cortical cells in maize
root (6×103 colony forming units (CFU)/g ±3.11) improving dry biomass with high relative water content
(RWC) and leaf water potential (LWP) compared to control. Inoculation with MZ30V92 downregulated
drought-responsive genes (27) like dehydrins, antioxidative genes, ethylene (ET) and abscisic
acid (ABA) regulators in roots and leaves of Zea mays as compared to uninoculated plants under
drought stress. There was no significant difference in the transcription of dehydration responsive genes
in inoculated tissues (root and leaves) compared to uninoculated under no-stress.
Conclusion: Endophyte MZ30V92 is active inside the plant tissue and primes the plant by downregulating
drought stress genes and alleviating drought stress effects. This report shows the potential of endophytic
bacteria in alleviating drought stress effects in maize.