Nitrogen deficiency as well as phosphorus deficiency in sorghum promotes the production and exudation of 5-deoxystrigol, the host recognition signal for arbuscular mycorrhizal fungi and root parasites

Abstract

Strigolactones released from plant roots induce hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi and germination of root parasitic weeds, Striga and Orobanche spp. We already demonstrated that, in red clover plants (Trifolium pratense L.), a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Ca, Mg) in the culture medium significantly promoted the secretion of a strigolactone, orobanchol, by the roots of this plant. Here we show that in the case of sorghum [Sorghum bicolor (L.) Moench], a host of both the root hemiparasitic plant Striga hermonthica and AM fungi, N deficiency as well as P deficiency markedly enhanced the secretion of a strigolactone, 5-deoxystrigol. The 5-deoxystrigol content in sorghum root tissues also increased under both N deficiency and P deficiency, comparable to the increase in the root exudates. These results suggest that strigolactones may be rapidly released after their production in the roots. Unlike the situation in the roots, neither N nor P deficiency affected the low content of 5-deoxystrigol in sorghum shoot tissues.

Kin recognition is a nutrient-dependent inducible phenomenon

“…31 Resource scarcity is also a major driving force in competition and can alter root exudate composition, the source of the signals responsible for KR. 26,30,32,33 Our findings support our hypothesis that nutrient availability modulates changes in the RSA associated with KR. Nutrient reduction resulted in a general increase in lateral root number, our metric for 'competition' in all samples.…”

“…24,25 Nutrient availability also alters exudate production and composition with the potential to impact both interorganismal interactions as well as nutrient uptake. [26][27][28][29] For example, in Sorghum bicolor reduced nitrogen and phosphorus levels promote the release of 5-deoxystrigol which encourages the recruitment of mycorrhizal fungi. 26 Clearly, plants must integrate information regarding both neighbor identity as well as nutrient availability if they are to successfully compete in the environment.…”

“…[26][27][28][29] For example, in Sorghum bicolor reduced nitrogen and phosphorus levels promote the release of 5-deoxystrigol which encourages the recruitment of mycorrhizal fungi. 26 Clearly, plants must integrate information regarding both neighbor identity as well as nutrient availability if they are to successfully compete in the environment. Work by Cahill et al with Abutilon theophrasti (Velvetleaf) suggested that when grown in isolation these plants preferred to adopt a broad rooting strategy regardless of nutrient avaialbility.…”

“…[22][23][24][25][26][27][28][29] Based on these prior observations we hypothesized that A. thaliana may utilize information regarding nutrient availability to influence decisions regarding competition based on neighbor identity. In other words, nutrient availability may influence the production of specific exudates associated with KR which could alter the RSA accordingly.…”

Root starch accumulation in response to arbuscular mycorrhizal colonization differs among Lotus japonicus starch mutants

“…Since AM fungi also represent a carbon cost to the plant, it is of utmost importance to characterize and understand the molecular components involved in the mutual exchange of nutrients and their impact on plant physiology and productivity (Sawers et al 2008). While transcriptomics and genetics studies have provided convincing evidence that the AM fungus plays an important role in plant P and N uptake (Balestrini et al 2007;Javot et al 2007;Gomez et al 2009;Guether et al 2009a;Branscheid et al 2010) and indicate how the nutrient status of the plant influences AM development (Javot et al 2007;Yoneyama et al 2007;Nagy et al 2009;Breuillin et al 2010), information on the molecular components important for carbon transfer to the fungus and carbon metabolism in mycorrhizal plants remains rather patchy (Franken 2010). …”