Abstract
Nostoc is widely known for its ability to fix atmospheric nitrogen and the establishment of symbiotic relationship with a wide range of plants from various taxonomic groups. Several strains of Nostoc produce phytohormones that promote growth of its plant partners. Nostoc OS-1 was therefore selected for study because of the presence of putative ipdC gene that encodes a key enzyme to produce Indole-3-acetic acid (IAA). The results indicated that both cellular and released IAA was found high with increasing incubation time and reached to a peak value (i.e., 21 pmol mg-1ch-a) on the third week as determined by UPLC-ESI-MS/MS. Also the Nostoc OS-1 strain efficiently colonized the roots and promoted the growth of rice as well as wheat under axenic conditions and induced ipdC gene that suggested the possible involvement of IAA in these phenotypes. To confirm the impact of IAA on root colonization efficiency and plant promoting phenotypes of Nostoc OS-1, an ipdC knockout mutant was generated by homologous recombinant method. The amount of releasing IAA, in vitro growth, root colonization, and plant promoting efficiency of the ipdC knockout mutant was observed significantly lower than wild type strain under axenic conditions. Importantly, these phenotypes were restored to wild-type levels when the ipdC knockout mutant was complemented with wild type ipdC gene. These results together suggested that ipdC and/or synthesized IAA of Nostoc OS-1 is required for its efficient root colonization and plant promoting activity.
Highlights
Co-existence has evolved in several forms of living organisms for successful life on the planet earth
Growth of cyanobacterial colonies started on the 6th day of the incubation of root segments on BG11 agar plates and the majority of the isolates (4 out of 7) were identified as Nostoc when their morphology was studied under a light microscope
Being renowned for its symbiotic association with plants, Nostoc was chosen to study their efficacy of colonization on plant roots as affected by self-produced Indole-3-acetic acid (IAA)
Summary
Co-existence has evolved in several forms of living organisms for successful life on the planet earth. Nostoc is a genus of nitrogen fixing cyanobacteria found in a number of environmental niches. Colonies of Nostoc are composed of filaments of moniliform cells embedded in a gelatinous sheath. Members of this genus associate symbiotically with diverse taxonomic groups of organisms (such as algae, Bryophytes, Pteridophytes, gymnosperms and angiosperms), benefiting their hosts with nitrogen in the form of nitrates (Rai and Bergman, 2000). In addition to nitrogen and carbon fixation (Adams and Duggan, 2012), symbiotic Nostoc can release phytohormones Indole-3-acetic acid (IAA and cytokinins), which improve plant vigor (Hussain et al, 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
