Endophytic colonization of rice (Oryza sativa L.) by the diazotrophic bacterium Burkholderia kururiensis and its ability to enhance plant growth

Abstract

Burkholderia kururiensis is a diazotrophic bacterium originally isolated from a polluted aquifer environment and presents a high level of similarity with the rice endophyte "B. brasilensis" species. This work assessed the ability of B. kururiensis to endophytically colonize rice plantlets by monitoring different tissues of root-inoculated plants for the presence of bacterial growth in different media, electron microscopy and by 16S rDNA analysis. Observations of roots, stems and leaves of inoculated rice plantlets by electron microscopy revealed B. kururiensis colonization predominantly on root hair zones, demonstrating endophytic colonization primarily through the endodermis, followed by spreading into xylem vessels, a possible pathway leading to aerial parts. Although indifferent for the bacterial growth itself, addition of a nitrogen source was a limiting factor for endophytic colonization. As endophytic colonization was directly associated to an enhanced plant development, production of phytohormone auxin/indole-3-acetic acid by B. kururiensis was assayed with transgenic rice plantlets containing an auxin-responsive reporter (DR5-GUS). Our findings suggest the ability of auxin production by plant-associated B. kururiensis which may have a stimulatory effect on plant development, as evidenced by activation of DR5-GUS. We hereby demonstrate, for the first time, the ability of B. kururiensis to endophytically colonize rice, promoting both plant growth and rice grain yield.

Burkholderia Species Are Major Inhabitants of White Lupin Cluster Roots

“…Burkholderia sequences retrieved from mature roots were phylogenetically diverse, despite the extremely selective environment (low pH and large amounts of citrate). Most sequences were closely related to B. kururiensis, a species first isolated from a polluted aquifer (43) and later observed to fix nitrogen and promote rice growth (24). However, other sequences retrieved from the mature stage were also found in phylogenetic clusters harboring sequences from juvenile and senescent origins.…”

Studies on endophytic Burkholderia sp. from sugarcane and its screening for plant growth promoting potential

“…Higher amount of IAA production increases lateral and adventitious root formation but inhibits the primary root growth (Xie et al, 1996), which is exactly what is needed for root development from sugarcane sett when planted. The production of IAA in B. vietnamiensis has been described by Govindarajan et al (2008) and in B. kururiensis (rice plant endophyte) by Mattos et al (2008). Production of GA by Burkholderia sp.…”

Mechanisms Controlling the Expression of the Exopolysaccharide of Burkholderia and Role in Niche Adaptation

“…Bacteria belonging to this second cluster have the ability to colonize the rhizosphere or the internal intercellular spaces in several plants. Some species were shown to promote plant growth, such as B. kururiensis and B. phytofirmans, and others to increase plant nutrient availability via nitrogen fixation and/or phosphate solubilization, like B. unamae, B. tropica and B. silvatlantica (Caballero-Mellado et al, 2007;Mattos et al, 2008;Perin et al, 2006;Reis et al, 2004). Many species have the ability to form symbiotic interactions with plants or with mosses, like B. tuberum, B. phymatum, B. mimosarum, B. nodosa, B. sabiae, B. megapolitana and B. bryophila (Chen et al, 2007;Chen et al, 2008;Elliott et al, 2007;Vandamme et al, 2002a).…”