Nitrogen deficiency influences strigolactone levels in basal parts of shoots and shoot branching phenotype in Arabidopsis thaliana

Strigolactones (SLs) are allelochemicals attracting both symbiotic arbuscular mycorrhizal (AM) fungi and root parasitic plants and a novel class of phytohormones inhibiting lateral shoot branching. In general, nutrient deficiency significantly promotes SL production in roots and exudation into the rhizosphere, and also induces suppressed shoot branching phenotype in host plants of AM fungi including rice, tomato, maize, etc. Nutrient deficiencies also inhibit the shoot branching in Arabidopsis thaliana (hereafter Arabidopsis), a non-host of AM fungi, while the level of carlactone, a non-canonical SL and the SL precursor for the other SLs, was reported to be unaffected. Because Arabidopsis SLs including CL and methyl carlactonoate,, are highly unstable, relationships between SL levels and shoot branching in Arabidopsis remain elusive. Herein, we demonstrate that nitrogen deficiency increases SL levels in the basal part of shoots in Arabidopsis and lateral shoot branching appears to be strongly regulated by these SLs.