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The antibiotic 2,4-diacetylphoroglucinol (2,4-DAPG), produced by the Gram-negative rod-shaped bacterium Pseudomonas fluorescens 2P24, is active against various soil-borne bacterial and fungal pathogens that cause plant diseases. Biosynthesis of 2,4-DAPG is controlled by regulating expression of the phlACBD operon at the post-transcriptional level. The phlG gene is located between the phlF and phlH genes, upstream of the phlACBD biosynthetic operon. Herein, we cloned the phlG gene, generated a phlG deletion mutant, and investigated its regulatory role in 2,4-DAPG biosynthesis. The results showed that deletion of phlG had no effect on the biosynthesis of 2,4-DAPG, but it affected conversion of 2,4-DAPG to its precursor monoacetylphloroglucinol (MAPG). The global regulatory factor encoded by gacS positively regulated expression of phlG, while rsmE negatively regulated its expression. Deleting phlG did not alter the ability of the bacterium to colonise plants or promote plant growth. these results suggest that phlG collaborates with other factors to regulate production of the antibiotic 2,4-DAPG in P. fluorescens 2P24. The antibiotic 2,4-diacetylphloroglucinol (DAPG) is produced by several Pseudomonas sp., including 2P24, CHA0, Pf-5, and YGJ3, and it plays a key role in inhibiting the growth of pathogenic microorganisms surrounding the plant rhizosphere 1-4. As a phenolic secondary metabolite, 2,4-DAPG from some bacteria above has shown the capacity to control various plant pathogens. For example, P. fluorescens CHA0 protects plants against tobacco black root rot, P. fluorescens F113 protects sugar beet against Pythium damping-off, and P. fluorescens 2P24 protects against tomato bacterial wilt and wheat take-all diseases 5-11. To further improve its potential applications, chemically synthesised 2,4-DAPG analogues have been developed and tested against plant diseases, and MP4, one of analogue of 2,4-DAPG, exhibited particularly potent antifungal activity, with inhibition rates of 84% and 63% against Penicillium. digitatum and Penicillium. italicum, respectively, and lower toxicity toward human cells compared with a fungicide widely used to treat harvested citrus fruit 12. Such discoveries may assist the utilisation of DAPG analogues as novel biological fungicides for controlling plant diseases. In P. fluorescens, the DAPG locus contains the four biosynthetic genes phlACBD that together produce 2,4-DAPG. PhlA, PhlC and PhlB are required for transacetylation of the monoacetylphloroglucinol (MAPG) precursor to generate DAPG 13,14 , and PhlD is critical for the biosynthesis of MAPG. In P. fluorescens 2P24, multiple factors in the GacS/GacA two-component system are involved in the biosynthesis of 2,4-DAPG during the late exponential and stationary phases 2,15,16. The small RNA-binding proteins RsmA and RsmE, the resistance-nodulation-division efflux pump EmhABC, and the sigma factors RpoD, RpoN and RpoS are also associated with 2,4-DAPG biosynthesis 1,17-21. In addition, PsrA is also a regulator of a sigma factor and invo...

No abstract

Rhinoncus sibiricus Faust, a major pest of buckwheat, has invaded the buckwheat cultivation areas of China for years. This pest was first found in Russia in 1940, causing great damage during the entire buckwheat-growing season. In China, there are few records on R. sibiricus, and studies regarding pest damage on buckwheat are unknown. The occurrence and distribution of this species in China is still not clear. We therefore conducted field surveys for 6 yr to identify the distribution range and the degree of pest damage caused by R. sibiricus in the buckwheat-planting areas of China and tested its preference for two Fagopyrum species in common garden experiments. The results showed that R. sibiricus had a larger distribution range in the Northern rather than the Southern part of China, and that pest damage was more serious in northern China. The pest preferred F. tataricum (Tartary buckwheat, Polygonales: Polygonaceae) over F. esculentum (Common buckwheat, Polygonales: Polygonaceae), but caused damage to both, indicating its potential for distribution in southern China. This study clarified the occurrence, distribution, and damage traits of R. sibiricus in the buckwheat cultivation areas of China, which will help explain the pest attack traits and inform strategies for pest control and prediction.

Potato (Solanum tuberosum L.) is an important vegetable crop that plays a pivotal role in the world, especially given its potential to feed the world population and to act as the major staple food in many developing countries. Every year, significant crop loss is caused by viral diseases due to a lack of effective agrochemical treatments, since only transmission by insect vectors can be combated with the use of insecticides, and this has been an important factor hindering potato production. With the rapid development of molecular biology and plant genetic engineering technology, transgenic approaches and non-transgenic techniques (RNA interference and CRISPR-cas9) have been effectively employed to improve potato protection against devastating viruses. Moreover, the availability of viral sequences, potato genome sequences, and host immune mechanisms has remarkably facilitated potato genetic engineering. In this study, we summarize the progress of antiviral strategies applied in potato through engineering either virus-derived or plant-derived genes. These recent molecular insights into engineering approaches provide the necessary framework to develop viral resistance in potato in order to provide durable and broad-spectrum protection against important viral diseases of solanaceous crops.