AUTHOR=Hussain Anwar , Shah Syed T. , Rahman Hazir , Irshad Muhammad , Iqbal Amjad 

TITLE=Effect of IAA on in vitro growth and colonization of Nostoc in plant roots

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00046

DOI=10.3389/fpls.2015.00046

ISSN=1664-462X

ABSTRACT=<p><italic>Nostoc</italic> 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 <italic>Nostoc</italic> produce phytohormones that promote growth of its plant partners. <italic>Nostoc</italic> OS-1 was therefore selected for study because of the presence of putative <italic>ipdC</italic> 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<sup>-1</sup>ch-<italic>a</italic>) on the third week as determined by UPLC-ESI-MS/MS. Also the <italic>Nostoc</italic> OS-1 strain efficiently colonized the roots and promoted the growth of rice as well as wheat under axenic conditions and induced <italic>ipdC</italic> 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 <italic>Nostoc</italic> OS-1, an <italic>ipdC</italic> knockout mutant was generated by homologous recombinant method. The amount of releasing IAA, <italic>in vitro</italic> growth, root colonization, and plant promoting efficiency of the <italic>ipdC</italic> knockout mutant was observed significantly lower than wild type strain under axenic conditions. Importantly, these phenotypes were restored to wild-type levels when the <italic>ipdC</italic> knockout mutant was complemented with wild type <italic>ipdC</italic> gene. These results together suggested that <italic>ipdC</italic> and/or synthesized IAA of <italic>Nostoc</italic> OS-1 is required for its efficient root colonization and plant promoting activity.</p>