Plants communicate with microorganisms by exchanging chemical signals throughout the phytosphere. Such interactions are important not only for plant productivity and fitness, but also for terrestrial ecosystem functioning. It is known that beneficial microorganisms emit diffusible substances including volatile organic compounds (VOCs) that promote growth. Consistently, soil application of cell-free culture filtrates (CF) of beneficial soil and plant-associated microorganisms enhances plant growth and yield. However, how this treatment acts in plants and whether it alters the resident soil microbiota, are largely unknown. In this work we characterized the responses of pepper (Capsicum annuum L.) plants cultured under both greenhouse and open field conditions and of soil microbiota to soil application of CFs of beneficial and phytopathogenic fungi. To evaluate the contribution of VOCs occurring in the CFs to these responses, we characterized the responses of plants and of soil microbiota to application of distillates (DE) of the fungal CFs. CFs and their respective DEs contained the same potentially biogenic VOCs, and application of these extracts enhanced root growth and fruit yield, and altered the nutritional characteristics of fruits. High-throughput amplicon sequencing of bacterial 16S and fungal ITS rRNA genes of the soil microbiota revealed that the CF and DE treatments altered the microbial community compositions, and led to strong enrichment of the populations of the same beneficial bacterial and fungal taxa. Our findings show that CFs of both beneficial and phytopathogenic fungi can be used as biostimulants, and provide evidence that VOCs occurring in the fungal CFs act as mediators of the plants' responses to soil application of fungal CFs through stimulation of the beneficial soil microbiota.

• Keywords
• biostimulant, fruit yield, fungal phytopathogen, plant growth promoting microorganism, plant-microbe interaction, soil microbiota, volatile organic compounds,
• Publication type
• Journal Article MeSH

Plant secondary metabolism evolved in the context of highly organized and differentiated cells and tissues, featuring massive chemical complexity operating under tight environmental, developmental and genetic control. Biotechnological demand for natural products has been continuously increasing because of their significant value and new applications, mainly as pharmaceuticals. Aseptic production systems of plant secondary metabolites have improved considerably, constituting an attractive tool for increased, stable and large-scale supply of valuable molecules. Surprisingly, to date, only a few examples including taxol, shikonin, berberine and artemisinin have emerged as success cases of commercial production using this strategy. The present review focuses on the main characteristics of plant specialized metabolism and their implications for current strategies used to produce secondary compounds in axenic cultivation systems. The search for consonance between plant secondary metabolism unique features and various in vitro culture systems, including cell, tissue, organ, and engineered cultures, as well as heterologous expression in microbial platforms, is discussed. Data to date strongly suggest that attaining full potential of these biotechnology production strategies requires being able to take advantage of plant specialized metabolism singularities for improved target molecule yields and for bypassing inherent difficulties in its rational manipulation.

• Keywords
• Genetically engineered cultures, In vitro culture, Natural products, Secondary metabolites, Synthetic biology,
• MeSH
• Artemisinins isolation & purification   metabolism   MeSH
• Axenic Culture MeSH
• Berberine isolation & purification   metabolism   MeSH
• Biological Products isolation & purification   metabolism   MeSH
• Biotechnology methods   MeSH
• Cell Culture Techniques MeSH
• Phytochemicals biosynthesis   isolation & purification   MeSH
• Metabolic Engineering methods   MeSH
• Naphthoquinones isolation & purification   metabolism   MeSH
• Paclitaxel biosynthesis   isolation & purification   MeSH
• Plant Cells chemistry   metabolism   MeSH
• Plants chemistry   genetics   metabolism   MeSH
• Secondary Metabolism MeSH
• Tissue Culture Techniques MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• artemisinin MeSH Browser
• Artemisinins MeSH
• Berberine MeSH
• Biological Products MeSH
• Phytochemicals MeSH
• Naphthoquinones MeSH
• Paclitaxel MeSH
• shikonin MeSH Browser