Wang Jianfeng, Zhang Yongqiang, Li Ying, Wang Xiaomin, Nan Wenbin, Hu Yanfeng, Zhang Hong, Zhao Chengzhou, Wang Feng, Li Ping, Shi Hongyong, Bi Yurong
Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, People's Republic of China.
Plant Cell Rep. 2015 Jun;34(6):1075-87. doi: 10.1007/s00299-015-1766-0. Epub 2015 Feb 21.
Endophytic microbes Bacillus sp. LZR216 isolated from Arabidopsis root promoted Arabidopsis seedlings growth. It may be achieved by promoting the lateral root growth and inhibiting the primary root elongation. Plant roots are colonized by an immense number of microbes, including epiphytic and endophytic microbes. It was found that they have the ability to promote plant growth and protect roots from biotic and abiotic stresses. But little is known about the mechanism of the endophytic microbes-regulated root development. We isolated and identified a Bacillus sp., named as LZR216, of endophytic bacteria from Arabidopsis root. By employing a sterile experimental system, we found that LZR216 promoted the Arabidopsis seedlings growth, which may be achieved by promoting the lateral root growth and inhibiting the primary root elongation. By testing the cell type-specific developmental markers, we demonstrated that Bacillus sp. LZR216 increases the DR5::GUS and DR5::GFP expression but decreases the CYCB1;1::GUS expression in Arabidopsis root tips. Further studies indicated that LZR216 is able to inhibit the meristematic length and decrease the cell division capability but has little effect on the quiescent center function of the root meristem. Subsequently, it was also shown that LZR216 has no significant effects on the primary root length of the pin2 and aux1-7 mutants. Furthermore, LZR216 down-regulates the levels of PIN1-GFP, PIN2-GFP, PIN3-GFP, and AUX1-YFP. In addition, the wild-type Arabidopsis seedlings in the present of 1 or 5 µM NPA (an auxin transport inhibitor) were insensitive to LZR216-inhibited primary root elongation. Collectively, LZR216 regulates the development of root system architecture depending on polar auxin transport. This study shows a new insight on the ability of beneficial endophytic bacteria in regulating postembryonic root development.
从拟南芥根部分离出的内生微生物芽孢杆菌属LZR216促进了拟南芥幼苗的生长。这可能是通过促进侧根生长和抑制主根伸长来实现的。植物根系定殖有大量微生物，包括附生微生物和内生微生物。研究发现它们有促进植物生长以及保护根系免受生物和非生物胁迫的能力。但关于内生微生物调节根系发育的机制却知之甚少。我们从拟南芥根部分离并鉴定出一种内生细菌芽孢杆菌属，命名为LZR216。通过采用无菌实验系统，我们发现LZR216促进了拟南芥幼苗的生长，这可能是通过促进侧根生长和抑制主根伸长来实现的。通过检测细胞类型特异性发育标记，我们证明芽孢杆菌属LZR216增加了拟南芥根尖中DR5::GUS和DR5::GFP的表达，但降低了CYCB1;1::GUS的表达。进一步研究表明，LZR216能够抑制分生组织长度并降低细胞分裂能力，但对根分生组织的静止中心功能影响不大。随后还发现，LZR216对pin2和aux1-7突变体的主根长度没有显著影响。此外，LZR216下调了PIN1-GFP、PIN2-GFP、PIN3-GFP和AUX1-YFP的水平。此外，在1或5 μM NPA（一种生长素运输抑制剂）存在的情况下，野生型拟南芥幼苗对LZR216抑制的主根伸长不敏感。总体而言，LZR216依赖于生长素极性运输来调节根系结构的发育。这项研究为有益内生细菌调节胚后根发育的能力提供了新的见解。
