Effect of Azospirillum brasilense Sp245 lipopolysaccharide on the functional activity of wheat root meristematic cells

Abstract

We studied changes in the physiological and biochemical parameters of wheat (Triticum aestivum L. 'Saratovskaya 29') seedlings treated with lipopolysaccharide isolated from the outer membrane of the associative bacterium Azospirillum brasilense Sp245. The obtained data were compared with (i) the results of plant inoculation with whole Sp245 cells and (ii) the effects exerted by the lipopolysaccharide and whole cells of the enterobacterium Escherichia coli K12 and the specific legume symbiont Rhizobium leguminosarum 249. The functional activity of meristematic cells was judged by their mitotic index and by the results of immunochemical determination of the proliferative antigen of initials, a molecular marker for wheat meristem cells. Treatment of the seedling root system with 10 μg mL −1 of Sp245 lipopolysaccharide increased the mitotic index (1.8-fold) and the antigen content (approximately 1.4-fold). These increases were comparable to the effects produced by whole cell inoculation (2-and 1.4-fold, respectively). Our findings give grounds to consider lipopolysaccharide as an active component of the Azospirillum cell surface that not only determines bacterial contact interactions with wheat roots but also participates in the induction of plant responses to these interactions. We finally discuss the linkage between the proliferative antigen of initials and the transduction of a hormonal signal to the cell, as well as the informational value of this antigen as an indicator of effectiveness of plant-bacterial interactions.

Improved potato microclonal reproduction with the plant growth-promoting rhizobacteria Azospirillum

“…On day 20 of growth, the mitotic index of the meristematic cells of the inoculated Kondor plants was about 2-fold higher than that for the controls: 2.3 vs. 1.3 % (LSD 0.05 =0.2 %). This finding is consistent with our previous data from a study of wheat seedling inoculation in vivo (Evseeva et al 2011) and with the data of Levanony and Bashan (1989). It is possible that the mitotic activity enhancement activated the morphogenetic program of development of regenerated plants, which is what we observed in recording the morphological characteristics of the inoculated plants on day 20 of growth (Table 1).…”

“…2 Detection of A. brasilense Sp245 in the microbiological test (a) and in the immunochemical assay system (b) for the Kondor potato cultivar. A: 1, 2, 3, root segments from 20-day-old potato microclones grown in vitro; B: 1, 2, 3, extracts from the bacteria that had grown around the corresponding root segments; 4, extract from A. brasilense Sp245 cells (positive control); 5, antibodies; 6, phosphate-buffered saline (negative control) Evseeva et al 2011). Ultimately, this leads to better rooting of microclones in pot soil, better survival in the field, accelerated biomass accumulation, and increased tuber yield.…”

Application of Azospirillum brasilense Lipopolysaccharides to Promote Early Wheat Plant Growth and Analysis of Related Biochemical Responses

“…Although the role of rhizobacterial LPS as a key component in the growth-promoting interactions between plants and bacteria awaits additional characterization, Evseeva et al (2011) reported that treatment of wheat roots seedlings with 10 µg A. brasilense Sp245 LPS increased the mitotic index of cells to a degree that was comparable to that produced by inoculation with whole cells, suggesting that LPS-mediated effects on plant growth may be related to their ability to induce cell division.…”

Wheat cultivars submitted to seed inoculation with Azospirillum brasilense and nitrogen application in different environments

“…In addition to the BNF ability, other mechanisms of growth promotion by Azospirillum are reported in the literature, such as the production of nitric oxide and increased activity of the enzyme ACC deaminase, besides the production of plant growth regulators such as auxins (Bhattacharyya & Jha, 2012). These regulators interfere with plant growth by increasing root system growth, allowing the exploration of a larger soil volume and increasing nutrient and water uptake (Evseeva et al, 2011).…”