Plant hormones (Literature sources on phytohormones and plant signalling)

Authors: Tao Wang, Jing Guo, Yaqi Peng, Xiangguang Lyu, Bin Liu, Shiyong Sun and Xuelu Wang.

Science (2021)

Editor's view: Nitrogen fixation in legume roots - Soybeans and other legumes form symbiotic relationships with nitrogen-fixing bacteria in root nodules, thus ensuring the plant a ready supply of the necessary nutrient. Wang et al. worked out the signaling pathways that integrate above-ground light with below-ground root nodulation. Two mobile regulators move from shoot to root in response to light and, together, they form a signaling module in the root that induces the expression of nodulation factors. Thus, when the shoot sees enough light to support photosynthetic productivity, the root gets the signal to ramp up nitrogen fixation

Abstract: "Symbiotic nitrogen fixation is an energy-expensive process, and the light available to plants has been proposed to be a primary influencer. We demonstrate that the light-induced soybean TGACG-motif binding factor 3/4 (GmSTF3/4) and FLOWERING LOCUS T (GmFTs), which move from shoots to roots, interdependently induce nodule organogenesis. Rhizobium-activated calcium- and calmodulin-dependent protein kinase (CCaMK) phosphorylates GmSTF3, triggering GmSTF3–GmFT2a complex formation, which directly activates expression of nodule inception (NIN) and nuclear factor Y (NF-YA1 and NF-YB1). Accordingly, the CCaMK–STF–FT module integrates aboveground light signals with underground symbiotic signaling, ensuring that the host plant informs its roots that the aboveground environment is prepared to sustainably supply the carbohydrate necessary for symbiosis. These results suggest approaches that could enhance the balance of carbon and nitrogen in the biosphere."