title: Euphorbia milii-native bacteria interactions under airborne formaldehyde stress: Effect of epiphyte and endophyte inoculation in relation to IAA, ethylene and ROS levels.
abstract: Better understanding of plant-bacteria interactions under stress is of the prime importance for enhancing airborne pollutant phytoremediation. No studies have investigated plant-epiphyte interactions compared to plant-endophyte interactions under airborne formaldehyde stress in terms of plant Indole-3-acetic acid (IAA), ethylene, reactive oxygen species (ROS) levels and pollutant removal efficiency. Euphorbia milii was inoculated with native plant growth-promoting (PGP) endophytic and epiphytic isolates individually to investigate plant-endophyte compared to plant-epiphyte interactions under continuous formaldehyde fumigation. Under airborne formaldehyde stress, endophyte interacts with its host plant closely and provides higher levels of IAA which protected the plant against formaldehyde phytotoxicity by lowering intracellular ROS, ethylene levels and maintaining shoot epiphytic community; hence, higher pollutant removal. However, plant-epiphyte interactions could not provide enough IAA to confer protection against formaldehyde stress; thus, increased ROS and ethylene levels, large decrease in shoot epiphytic population and lower pollutant removal although epiphyte contacts with airborne pollutant directly (has greater access to gaseous formaldehyde). Endophyte-inoculated plant synthesized more tryptophan as a signaling molecule for its associated bacteria to produce IAA compared to the epiphyte-inoculated one. Under stress, PGP endophyte interacts with its host closely; thus, better protection against stress and higher pollutant removal compared to epiphyte which has limited interactions with the host plant; hence, lower pollutant removal.
authors.affiliation: School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand. Electronic address: Gholamreza.biotech@mail.kmutt.ac.th.
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Khaksar
authors.affiliation: Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand. Electronic address: Chairat.tre@kmutt.ac.th.
authors.forename: Chairat
authors.initials: C
authors.lastname: Treesubsuntorn
authors.affiliation: School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkok 10150, Thailand. Electronic address: paitip.thi@kmutt.ac.th.
authors.forename: Paitip
authors.initials: P
authors.lastname: Thiravetyan
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D015169:Colony Count, Microbial; D060026:Endophytes / Q000187:drug effects / Q000502:physiology; D005030:Ethylenes / Q000378:metabolism*; D028481:Euphorbia / Q000382:microbiology*; D005557:Formaldehyde / Q000633:toxicity*; D007210:Indoleacetic Acids / Q000378:metabolism*; D018520:Plant Shoots / Q000187:drug effects / Q000382:microbiology; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects*; D014364:Tryptophan / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D005030:Ethylenes; D007210:Indoleacetic Acids; D017382:Reactive Oxygen Species; D002734:Chlorophyll; D005557:Formaldehyde; C030737:indoleacetic acid; D014364:Tryptophan; C036216:ethylene
keywords: Airborne formaldehyde; Ethylene; Euphorbia milii; Indole-3-acetic acid (IAA); Plant-bacteria interactions; Reactive oxygen species (ROS); Tryptophan