Abstract
Nodulation process in legume plants is essential for biological nitrogen fixation during which process a large amount of phosphorus (P) is required. Under P deficiency, nodule formation is greatly affected, and induction of purple acid phosphatases (PAPs) is an adaptive strategy for nodules to acquire more P. However, regulation roles of PAPs in nodules remain largely understood. In this study, by transcriptome sequencing technology, five PAP genes were found to be differentially expressed, which led to the greatly increased acid phosphatase (APase) and phytase activities in soybean mature nodules under P starvation conditions; and among the five PAP genes, GmPAP12 had the highest transcript level, and RT-PCR indicated expression of GmPAP12 was gradually increasing during nodule development. GUS activity driven by GmPAP12 promoter was also significantly induced in low phosphorus conditions. Further functional analysis showed that under low phosphorus stress, overexpression of GmPAP12 resulted in higher nodule number, fresh weight, and nitrogenase activity as well as the APase activity than those of control plant nodules, whereas the growth performance and APase activity of nodules on hairy roots were greatly lower when GmPAP12 was suppressed, indicating that GmPAP12 may promote P utilization in soybean nodules under low P stress, which thus played an important role in nodulation and biological nitrogen fixation. Moreover, P1BS elements were found in the promoter of GmPAP12, and yeast one-hybrid experiment further proved the binding of P1BS by transcription factor GmPHR1 in the promoter of GmPAP12. At last, overexpression and suppression of GmPHR1 in nodules indeed caused highly increased and decreased expression of GmPAP12, respectively, indicating that GmPAP12 is regulated by GmPHR1 in soybean nodules. Taken together, these data suggested that GmPAP12 was a novel soybean PAP involved in the P utilization and metabolism in soybean root nodules and played an important role in the growth and development of root nodules and biological nitrogen fixation.
Highlights
Legumes, such as soybean (Glycine max), pea (Pisum sativum), common bean (Phaseolus vulgaris), alfalfa (Medicago sativa), and chickpea (Cicer arietinum L.), interact with specific soil nitrogen (N)-fixing rhizobia to develop symbiotic relationships that result in the formation of a new organ called root nodules (Oldroyd and Downie, 2008; Ferguson et al, 2010)
P content in shoot and root was dramatically reduced by 72.5 and 82.2% respectively, in nodules, it was decreased by only 20.8%, which was less strong in low P stress than in high P conditions (Figure 1F)
These data suggested that low P supply affected soybean nodulation and that P homeostasis was very important for soybean growth and symbiotic N2 fixation
Summary
Legumes, such as soybean (Glycine max), pea (Pisum sativum), common bean (Phaseolus vulgaris), alfalfa (Medicago sativa), and chickpea (Cicer arietinum L.), interact with specific soil nitrogen (N)-fixing rhizobia to develop symbiotic relationships that result in the formation of a new organ called root nodules (Oldroyd and Downie, 2008; Ferguson et al, 2010). Soybean nodules can fix atmospheric N2 via rhizobia that provide plants with nitrogen source for growth in rotation systems, which is an efficient way to sustain agricultural system due to symbiotic nitrogen fixation (SNF). The availability of N for plants is very limited in soils that restrict the production of crops To deal with this situation, agriculture has been largely reliant on nitrogen fertilizers to maximize the crop productivity with about 50% of the nitrogen fertilizers leaching into aquatic system, resulting in environmental pollution. It is urgent to find an alternative and effective way to provide nitrogen available for soybean growth; at the moment, biological nitrogen fixation in legume nodules arises as being one of the most hot issues in the world (Oldroyd, 2007; Marx et al, 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
