Greetatorn T, Hashimoto S, Sarapat S, Tittabutr P, Boonkerd N, Uchiumi T, Teaumroong N
School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
Graduate School of Science and Engineering, Kagoshima University, Kagoshima, Japan.
Lett Appl Microbiol. 2019 Mar;68(3):258-266. doi: 10.1111/lam.13114. Epub 2019 Feb 6.
Bradyrhizobium sp. strain SUTN9-2 was confirmed as rice endophytic bacteria and also as rice growth promotion agent. SUTN9-2 showed the capability of plant growth promotion characteristics, such as indole-3-acetic acid (IAA) and 1-amino-cyclopropane-1-carboxylic acid (ACC) deaminase productions and nitrogen fixation. In this study, the ability of SUTN9-2 to stimulate rice growth was investigated at different stages with N-free and NH NO under in vivo condition. The rice dry weight and chlorophyll content could be enhanced when SUTN9-2 was inoculated in N-free, especially at seedling stage (7 and 14 dai). The rice dry weight was also increased when SUTN9-2 was inoculated with NH NO at 7 and14 dai. The results of quantitative analysis of IAA and ACC deaminase were inconsistent with the expression of genes involved in IAA (nit) and ACC deaminase (acdS) productions. This inconsistently could implied that IAA and ACC deaminase produced from SUTN9-2 do not directly affect rice growth, but other factors resulting from the production of IAA and ACC deaminase could be involved. Moreover, the expression of genes involved in nitrogen fixation (nifH and nifV) of SUTN9-2 was also induced in rice tissues. This finding suggested that rice growth promotion may be supported by NH NO together with nitrogen fixation by SUTN9-2. SIGNIFICANCE AND IMPACT OF THE STUDY: Indole-3-acetic acid, 1-amino-cyclopropane-1-carboxylic acid deaminase productions and nitrogen fixation may play important roles in rice growth promotion by endophytic SUTN9-2, especially at early rice seedling growth stage, which has the potential to be used as rice seedling growth promoter in the system of rice intensification.
慢生根瘤菌属菌株SUTN9-2被确认为水稻内生细菌，也是一种水稻生长促进剂。SUTN9-2表现出促进植物生长的特性，如产生吲哚-3-乙酸（IAA）和1-氨基环丙烷-1-羧酸（ACC）脱氨酶以及固氮能力。在本研究中，在无氮和硝酸铵条件下，于体内条件下研究了SUTN9-2在不同阶段刺激水稻生长的能力。当在无氮条件下接种SUTN9-2时，水稻干重和叶绿素含量会增加，尤其是在幼苗期（接种后7天和14天）。在接种后7天和14天接种硝酸铵时，SUTN9-2也会使水稻干重增加。IAA和ACC脱氨酶的定量分析结果与参与IAA（nit）和ACC脱氨酶（acdS）产生的基因表达不一致。这种不一致可能意味着SUTN9-2产生的IAA和ACC脱氨酶不会直接影响水稻生长，但IAA和ACC脱氨酶产生的其他因素可能参与其中。此外，SUTN9-2中参与固氮（nifH和nifV）的基因表达也在水稻组织中被诱导。这一发现表明，硝酸铵与SUTN9-2的固氮作用可能共同促进水稻生长。研究的意义和影响：吲哚-3-乙酸、1-氨基环丙烷-1-羧酸脱氨酶的产生和固氮可能在内生菌SUTN9-2促进水稻生长中发挥重要作用，尤其是在水稻幼苗生长早期，其有潜力在水稻强化栽培体系中用作水稻幼苗生长促进剂。
