ABSTRACT
Plant species diversity is one of the critical factors for maintaining multi-function and stability of terrestrial ecosystem. We reviewed the traditional methods for measuring plant species diversity of grassland (PSDG), and then introduced the new ideas and methods used for PSDG monitoring. Traditionally, PSDG monitoring depended heavily on ground-based investigation, which usually required large amounts of time, labor, and cost, and therefore was only suitable for small scale investigation. Grassland plant species were typically small in size and highly mixed. It was difficult to identify and measure by remote sensing due to the limitation of resolution. Consequently, most studies on PSDG were based on remote-sensing retrieval or habitat simulation. Characterized with high spatial-temporal resolution, flexible and low cost, the unmanned aerial vehicle (UAV) technology was regarded as the bridge between ground-based investigation and satellite remote sensing. It could be the breakthrough for monitoring PSDG accurately at large scales. In the future, we should establish PSDG monitoring network by combining the fixed monitoring sites and dynamic monitoring sites of UAV and satellite remote sensing, and integrating UAV and automatic target recognition organically.
Subject(s)
Ecosystem , Remote Sensing Technology , Grassland , Remote Sensing Technology/methodsABSTRACT
BACKGROUND: Agrobacterium rhizogenes-mediated hairy root transformation provides a powerful tool for investigating the functions of plant genes involved in rhizobia-legume symbiosis. However, in the traditional identification methods of transgenic hairy roots based on reporter genes, an expensive chemical substrate or equipment is required. RESULTS: Here, we report a novel, low cost, and robust reporter for convenient, non-destructive, and directly visual selection of transgenic hairy roots by naked eye, which can be used in the study of rhizobia-legume symbiosis. The reporter gene AtMyb75 in Arabidopsis, encoding an R2R3 type MYB transcription factor, was ectopically expressed in hairy roots-mediated by A. rhizogenes, which induced purple/red colored anthocyanin accumulation in crop species like soybean (Glycine max (L.) Merr.) and two model legume species, Lotus japonicas and Medicago truncatula. Transgenic hairy roots of legumes containing anthocyanin can establish effective symbiosis with rhizobia. We also demonstrated the reliability of AtMyb75 as a reporter gene by CRISPR/Cas9-targeted mutagenesis of the soybean resistance to nodulation Rfg1 gene in the soybean PI377578 (Nod-) inoculated with Sinorhizobium fredii USDA193. Without exception, mature nitrogen-fixation nodules, were formed on purple transgenic hairy roots containing anthocyanin. CONCLUSIONS: Anthocyanin is a reliable, user-friendly, convenient, non-destructive, low cost, directly visual reporter for studying symbiotic nitrogen-fixing nodule development and could be widely applied in broad leguminous plants.
