PGPR菌株Tsukamurella sp. P9、Burkholderia sp. P10与花生互作机制的比较研究

Plant-growth-promoting rhizobacteria (PGPR) are a group of microbes which colonize the plant roots, exerting beneficial effects on plant development. However, there are few studies focus on actinomyces. We have isolated and screened two rhizosphere microbes P9 and P10, with good abilities to phosphate solubilization and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Meanwhile, there were evident growth-promoting effects on the fresh weight, plant height, root weight of peanuts inoculated with P9, P10 alone by pot experiment. The strain P9, P10 were identified as Tsukamurela sp. and Burkholderia sp. by 16S rRNA gene amplication and blast analysis. And this finding for the first time that Tsukamurela sp. could improve plant growth. In this study, The P9, P10 strain is being inoculated alone or co-inoculated with peanuts. Root colonization will be studied with gfp or rfp gene tagged strain. The peanut transcriptome will be performed by RNA-Seq after exposure to this two strains. And whole transcription analysis of P9, P10 will be studied after treated with peanut root exaduates, too. In addition, plant resistance and induced systemic resistance (ISR) against abiotic stress are being monitored with physiological properties and antioxidant enzymatic acitivity of treated peanuts. Then soil microbial ecology and soil fertility will be evaluated after treated with the two PGPR strains. In general, we should carry out integrative analyses on the relationship of “PGPR- rhizosphere- peanut” by physiological, ecological and transcriptomics studies, and interaction mechanisms between Tsukamurella sp. P9, Burkholderia sp. P10 and peanut will be revealed at all.

PGPR菌株可促进植物生长，但具促生作用的放线菌研究很少。项目前期筛选到2株促生菌P9和P10，均有较高的ACC脱氨酶活性和溶磷能力，对盆栽花生促生效应显著。本项目拟利用首次发现具促生作用的放线菌Tsukamurela sp. P9、与细菌Burkholderia sp. P10进行单一接种或复合菌株共接种研究，通过荧光标记法探索菌株在花生根际的定殖规律；转录组学比较分析花生根部响应菌株的模式，及P9、P10菌株受根系分泌物作用后的基因表达模式差异，寻求菌株与花生互作关键基因；通过对植株生理特性及抗氧化酶活研究以分析花生抗逆性；并进行接种后土壤微生物结构功能及理化性质的影响研究。总之，从整体上研究“PGPR菌株-根际-花生”的关系，综合生理学、转录组学及生态学研究方法，从根本上解析Tsukamurella sp. P9、Burkholderia sp. P10与花生互作机制的差异。

本项目以分离筛选到的、对花生促生的耐酪氨酸束村氏菌(Tsukamurella tyrosinosolvens) P9和吡咯伯克霍尔德氏菌(Burkholderia pyrrocina) P10进行研究，发现利福平标记及GFP标记的2个菌株可以稳定定殖在花生的根茎组织、且P10的竞争定殖能力强于P9。花生的根系分泌物不仅通过上调2个菌株的物质转运及营养代谢通路而促进菌株生长，诱导铁载体、有机酸的分泌增加而更好地发挥促生；而且还通过影响P9菌株产生抗生素及毒力因子，影响P10菌株分泌IAA及胞外多糖、调控细菌分泌系统、群体感应及两组分系统、影响鞭毛组装及细菌趋化性等不同代谢途径对菌株的促生及定殖产生有益影响。2个菌株的接种均可以促进花生幼苗的生长；在接种早期，植株通过多条信号通路上调而快速响应、乙烯生成增多、细胞壁组分降解为菌株定殖奠定基础，但P10菌株可致花生更强的光合作用；在接种后期，植株的物质代谢活跃，能量产生增多，赤霉素分泌增加，接种花生的生长加快。此外，2个菌株还可通过活化土壤微生物、影响根际土壤的细菌群落结构、提高有益微生物及功能微生物的数量和丰度，提高土壤和植株的营养元素而达到其促生效应。盐及干旱胁迫下，2个菌株的单一接种及共接种可以提高花生的抗氧化酶活、降低植株的丙二醛含量和H2O2含量，提高花生在干旱及盐胁迫下的抗性并促进逆境下的生长。项目解析了2个不同种属的PGPR菌株，即T. tyrosinosolvens P9和B. pyrrocina P10菌株与花生的促生互作机制，拓宽了束村氏菌属的生态学功能，且吡咯伯克霍尔德氏菌P10由于更强的定殖及抗逆能力，为其进一步应用奠定了坚实的理论基础。