No abstract

The major insight in this manuscript is that we identified a new flowering regulator, GmSOC1-like, which may participate in the initiation and maintenance of flowering in soybean. Flowering is pivotal for the reproductive behavior of plants, and it is regulated by complex and coordinated genetic networks that are fine-tuned by endogenous cues and environmental signals. To better understand the molecular basis of flowering regulation in soybean, we isolated GmSOC1 and GmSOC1-like, two putative soybean orthologs for the Arabidopsis SUPPRESSOR OF OVEREXPRESSION OF CO1/AGAMOUS-LIKE 20 (SOC1/AGL20). The expression pattern of GmSOC1-like was analyzed by qRT-PCR in Zigongdongdou, a photoperiod-sensitive soybean cultivar. GmSOC1-like was widely expressed at different levels in most organs of the soybean, with the highest expression in the shoot apex during the early stage of floral transition. In addition, its expression showed a circadian rhythm pattern, with the highest expression at midnight under short-day (SD) condition. Intriguingly, GmSOC1-like was induced 4 days earlier than GmSOC1 during flowering transition in SD, suggesting that GmSOC1 and GmSOC1-like expression might be differentially regulated. However, under long-day (LD) condition, the expression of GmSOC1 and GmSOC1-like decreased gradually in the shoot apex of Zigongdongdou, which is in accordance with the fact that Zigongdongdou maintains vegetative growth in LD. In addition, overexpression of GmSOC1-like stimulated the flowering of Lotus corniculatus cv. supperroot plants. In conclusion, the results of this study indicate that GmSOC1-like may act as a flowering inducer in soybean.

Rhizosphere microbial communities are of great importance to mediate global biogeochemical cycles, plant growth, and fitness. Yet, the processes that drive their assembly remain unclear. The perennial shrubs Caragana spp., which is well known for their role in soil and water conservation, provides an ideal system to study the biogeography of rhizosphere microorganism communities within natural ecosystems. In order to detect how bacterial rhizosphere communities vary in terms of community diversity and composition, the rhizosphere bacterial community of three Caragana species, Caragana microphylla Lam., C. liouana Zhao, and C. korshinskii Kom., which distributed in arid and semi-arid region of northern China were investigated. Across species, Proteobacteria (61.1%), Actinobacteria (16.0%), Firmicutes (8.6%), Bacteroidetes (3.0%), Acidobacteria (3.5%), Gemmatimonadetes (1.4%), and Cyanobacteria (1.0%) were the most dominant phyla in the rhizosphere of the three Caragana species. The relative abundance of Cyanobacteria was significantly higher in rhizosphere of C. korshinskii Kom. compared with C. microphylla Lam. and C. liouana Zhao, while the opposite was found for Gemmatimonadetes in rhizosphere of C. microphylla Lam. relative to C. liouana Zhao. Stepwise multiple linear regression analysis showed that both diversity and richness of the bacterial rhizosphere communities significantly and positively correlated with soil pH (p < 0.01). Distance-based redundancy analysis indicated that soil properties and non-soil parameters detected there accounted for 47.5% of bacterial phylogenetic structure variation (p < 0.01) all together. Meanwhile, soil total phosphorus accounted for the greatest proportion of community structure variance (9.7%, p < 0.01), followed by electrical conduction (6.5%), altitude (5.8%), soil pH (5.4%), mean annual precipitation (3.6%) and total nitrogen (3.6%, p < 0.05 in all cases). Furthermore, partial Mantel test suggested that bacterial rhizosphere community structure significantly correlated with geographical distance, indicating that the less geographical distant sample sites tend to harbor more similar bacterial rhizosphere community. Our results shed new light on the mechanisms of coevolution and interaction between long-lived plants and their rhizosphere bacterial communities across environmental gradients.