Histochemical Evidence for Nitrogen-Transfer Endosymbiosis in Non-Photosynthetic Cells of Leaves and Inflorescence Bracts of Angiosperms

Biology

Sharron Crane¹  April Micci²  Kathryn Kingsley²  Qiuwei Zhang²  Sean Lindert²  Peerapol Chiaranunt²  Matthew Elmore²  Xiaoqian Chang²  Linsey Park²  Raquele Strickland²  James F. White²  Fernando Velazquez²  Philip L. Vines²  David Johnston-Monje³  Ivelisse Irizarry⁴  Kurt P. Kowalski⁵ 

[1] Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA;Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901, USA;Max Planck Tandem Group in Plant Microbial Ecology, Universidad del Valle, Cali 760043, Colombia;School of Health and Sciences, Universidad del Sagrado Corazón, San Juan 00914, Puerto Rico;US Geological Survey Great Lakes Science Center, Ann Arbor, MI 48105, USA;

关键词: endophytes;    histochemistry;    nitrate;    nitrogen-use efficiency;    trichomes;    nuclei;   

DOI  :  10.3390/biology11060876

来源: DOAJ

【 摘 要 】

We used light and confocal microscopy to visualize bacteria in leaf and bract cells of more than 30 species in 18 families of seed plants. Through histochemical analysis, we detected hormones (including ethylene and nitric oxide), superoxide, and nitrogenous chemicals (including nitric oxide and nitrate) around bacteria within plant cells. Bacteria were observed in epidermal cells, various filamentous and glandular trichomes, and other non-photosynthetic cells. Most notably, bacteria showing nitrate formation based on histochemical staining were present in glandular trichomes of some dicots (e.g., Humulus lupulus and Cannabis sativa). Glandular trichome chemistry is hypothesized to function to scavenge oxygen around bacteria and reduce oxidative damage to intracellular bacterial cells. Experiments to assess the differential absorption of isotopic nitrogen into plants suggest the assimilation of nitrogen into actively growing tissues of plants, where bacteria are most active and carbohydrates are more available. The leaf and bract cell endosymbiosis types outlined in this paper have not been previously reported and may be important in facilitating plant growth, development, oxidative stress resistance, and nutrient absorption into plants. It is unknown whether leaf and bract cell endosymbioses are significant in increasing the nitrogen content of plants. From the experiments that we conducted, it is impossible to know whether plant trichomes evolved specifically as organs for nitrogen fixation or if, instead, trichomes are structures in which bacteria easily colonize and where some casual nitrogen transfer may occur between bacteria and plant cells. It is likely that the endosymbioses seen in leaves and bracts are less efficient than those of root nodules of legumes in similar plants. However, the presence of endosymbioses that yield nitrate in plants could confer a reduced need for soil nitrogen and constitute increased nitrogen-use efficiency, even if the actual amount of nitrogen transferred to plant cells is small. More research is needed to evaluate the importance of nitrogen transfer within leaf and bract cells of plants.

【 授权许可】

Unknown