To overcome nitrogen deficiency, legume roots establish symbiotic interactions with nitrogen-fixing rhizobia that are fostered in specialized organs (nodules). Similar to other organs, nodule formation is determined by a local maximum of the phytohormone auxin at the primordium site. However, how auxin regulates nodule development remains poorly understood. Here, we found that in soybean, (Glycine max), dynamic auxin transport driven by PIN-FORMED (PIN) transporter GmPIN1 is involved in nodule primordium formation. GmPIN1 was specifically expressed in nodule primordium cells and GmPIN1 was polarly localized in these cells. Two nodulation regulators, (iso)flavonoids trigger expanded distribution of GmPIN1b to root cortical cells, and cytokinin rearranges GmPIN1b polarity. Gmpin1abc triple mutants generated with CRISPR-Cas9 showed the impaired establishment of auxin maxima in nodule meristems and aberrant divisions in the nodule primordium cells. Moreover, overexpression of GmPIN1 suppressed nodule primordium initiation. GmPIN9d, an ortholog of Arabidopsis thaliana PIN2, acts together with GmPIN1 later in nodule development to acropetally transport auxin in vascular bundles, fine-tuning the auxin supply for nodule enlargement. Our findings reveal how PIN-dependent auxin transport modulates different aspects of soybean nodule development and suggest that the establishment of auxin gradient is a prerequisite for the proper interaction between legumes and rhizobia.

• MeSH
• biologický transport MeSH
• Glycine max genetika   růst a vývoj   metabolismus   MeSH
• kořenové hlízky rostlin růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH
• rostlinné proteiny MeSH

UNLABELLED: Cytokinins (CKs) are involved in several developmental stages in the life-cycle of plants. The CK content in plants and their respective organs are susceptible to changes under different environmental conditions. In the current study, we profiled the CK content in the above and underground organs of three legumes (Lessertia frutescens, Mucuna pruriens and Pisum sativum) grown in soils collected from four locations (Ashburton, Bergville, Hluhluwe and Izingolweni) in KwaZulu-Natal province, South Africa. The quantified CK contents in the three legumes were categorized on the basis of their side chains (isoprenoid, aromatic and furfural) and modifications (e.g. free bases and glucosides). Legume and soil types as well as their interaction significantly influenced the concentrations of CKs. Lessertia frutescens, Mucuna pruriens and Pisum sativum had CK content that ranged from 124-653, 170-670 and 69-595 pmol/g DW, respectively. Substantial quantity (> 600 pmol/g DW) of CK were observed in plants grown in Bergville (above-ground part of Lessertia frutescens) and Izingolweni (underground part of Mucuna pruriens) soils. A total of 28 CK derivatives observed in the legumes comprised of isoprenoid (22), aromatic (5) and furfural (1) side-chain CKs. However, the 16 CK derivatives in Mucuna pruriens were isoprenoid-type based on the side-chain. Generally, a higher ratio of cis-zeatin (cZ) relative to the trans-zeatin (tZ) was evident in the above-ground part of Lessertia frutescens and Pisum sativum for the four soil treatments. In terms of functional and physiological importance of the CKs, the free bases (active form) and ribosides (translocation form) were the most abundant CK in Lessertia frutescens and Pisum sativum. However, N-glucoside, a deactivation/detoxicification product was the most dominant CK in Mucuna pruriens from Hluhluwe and Izingolweni soils. The total CKs in the underground parts of the legumes had a positive significant correlation with the total phosphorus and nitrogen content in the plant as well as the soil nitrogen. Overall, the CK profiles of the legumes were strongly influenced by the soil types. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01021-2.

• Klíčová slova
• Biomass, Fabaceae, Nitrogen fixation, Nodulation, Phytohormones, Rhizobia,
• Publikační typ
• časopisecké články MeSH