Gond S K, Torres M S, Bergen M S, Helsel Z, White J F
Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, USA; Department of Botany, Visva-Bharati, Santiniketan WB, India.
Lett Appl Microbiol. 2015 Apr;60(4):392-9. doi: 10.1111/lam.12385. Epub 2015 Jan 29.
Bacteria were isolated from surface disinfected seeds of eight modern corn types and an ancestor of corn, 'teosinte' and identified using 16S rDNA sequences. From each of the modern corn types we obtained Bacillus spp. (including, Bacillus amyloliquefaciens and Bacillus subtilis); while from teosinte we obtained only Pantoea agglomerans and Agrobacterium species. Of these bacteria, only P. agglomerans could actively grow under hypersaline conditions and increase salt tolerance of tropical corn seedlings. In laboratory and greenhouse experiments where plants were watered with a 0.2 mol l(-1) NaCl solution, P. agglomerans was found to enhance the capacity of tropical corn to grow compared to uninoculated controls. The total dry biomass was significantly higher in P. agglomerans-treated plants compared to controls under saline water. Gene expression analysis showed the up-regulation of the aquaporin gene family especially plasma membrane integral protein (ZmPIP) genes in P. agglomerans-treated plants. The plasma membrane integral protein type 2 (PIP2-1) gene in tropical corn seedlings was highly up-regulated by P. agglomerans treatment under salt stress conditions. Microscopic examination of P. agglomerans inoculated seedlings revealed that the bacterium colonized root meristems densely, and as roots developed, the bacterium became sparsely located in cell junctions.
The enhancement of salt tolerance capacity in tropical corn, an important food crop, has the capacity to increase its cultivation area and yield in saline soils. The application of rhizobacteria to improve salt tolerance of tropical corn is ecofriendly and cost effective. We show that P. agglomerans isolated from teosinte (an ancestor of corn) induces salt tolerance in tropical corn and up-regulation of aquaporin genes. This study shows that microbes that increase salt tolerance may be used to enhance crop growth in saline soils.
从8种现代玉米品种以及玉米的祖先“大刍草”经表面消毒的种子中分离出细菌，并使用16S rDNA序列进行鉴定。从每种现代玉米品种中我们获得了芽孢杆菌属（包括解淀粉芽孢杆菌和枯草芽孢杆菌）；而从大刍草中我们仅获得了成团泛菌和土壤杆菌属物种。在这些细菌中，只有成团泛菌能够在高盐条件下活跃生长，并提高热带玉米幼苗的耐盐性。在实验室和温室实验中，用0.2 mol l(-1) NaCl溶液浇灌植物，发现与未接种的对照相比，成团泛菌能增强热带玉米的生长能力。在盐水条件下，成团泛菌处理的植物总干生物量显著高于对照。基因表达分析表明，成团泛菌处理的植物中，水通道蛋白基因家族尤其是质膜内在蛋白（ZmPIP）基因上调。在盐胁迫条件下，成团泛菌处理使热带玉米幼苗中的质膜内在蛋白2型（PIP2 - 1）基因高度上调。对成团泛菌接种的幼苗进行显微镜检查发现，该细菌密集地定殖在根分生组织中，随着根的发育，该细菌稀疏地位于细胞连接处。
重要粮食作物热带玉米耐盐能力的增强，有能力扩大其在盐渍土壤中的种植面积并提高产量。应用根际细菌提高热带玉米的耐盐性既环保又经济有效。我们表明，从大刍草（玉米的祖先）中分离出的成团泛菌可诱导热带玉米产生耐盐性并上调水通道蛋白基因。这项研究表明，增加耐盐性的微生物可用于增强盐渍土壤中作物的生长。
