Moderately reducing N input to mitigate heat stress in maize.

In a warming climate, high temperature stress greatly threatens crop yields. Maize is critical to food security, but frequent extreme heat events coincide temporally and spatially with the period of kernel number determination (e.g., flowering stage), greatly limiting maize yields. In this context, how to increase or at least maintain maize yield has become more important. Nitrogen fertilizer (N) is widely used to improve maize yields, but its effect in heat stress is unclear. For this, we collected 1536 pairs of comparisons from 113 studies concerning N conducted in the past 20 years over China. We classified the data into two groups - without high temperature stress (NHT) and with high temperature stress during the critical period for maize kernel number determination (HT) - based on the national meteorological data. We comprehensively evaluated N effects on grain yield under HT and NHT using meta-analysis. The effect of N on maize yield became significantly smaller in HT than that in NHT. In NHT, soil characteristics, crop management practices, and climatic conditions all significantly affected N effects on maize yield, but in HT, only a few factors such as soil organic matter and mean annual precipitation significantly affected N effects. Hence, it is difficult to improve N effect by improving soil characteristics and crop management when meeting with high temperature stress during flowering. On average, N effect increased with increased N input, but there were respective N input thresholds in NHT and HT, beyond which N effects on maize yield remained stable. According to the thresholds, it is speculated that moderately reducing N input (~20 %) likely increased high temperature tolerance of maize during flowering. These findings have important implications for the optimization of N management under a warming climate.

Marked variations in diversity and functions of gut microbiota between wild and domestic stag beetle Dorcus Hopei Hopei.

BACKGROUND: Although stag beetles are a popular saprophytic insect, their gut microbiome has been poorly studied. Here, 16 S rRNA gene sequencing was employed to reveal the gut microbiota composition and functional variations between wild and domestic Dorcus hopei hopei (Dhh) larval individuals. RESULTS: The results indicated a significant difference between the wild and domestic Dhh gut microbiota., the domestic Dhh individuals contained more gut microbial taxa (e.g. genera Ralstonia and Methyloversatilis) with xenobiotic degrading functions. The wild Dhh possesses gut microbiota compositions (e.g. Turicibacter and Tyzzerella ) more appropriate for energy metabolism and potential growth. This study furthermore assigned all Dhh individuals by size into groups for data analysis; which indicated limited disparities between the gut microbiota of different-sized D. hopei hopei larvae. CONCLUSION: The outcome of this study illustrated that there exists a significant discrepancy in gut microbiota composition between wild and domestic Dhh larvae. In addition, the assemblage of gut microbiome in Dhh was primarily attributed to environmental influences instead of individual differences such as developmental potential or size. These findings will provide a valuable theoretical foundation for the protection of wild saprophytic insects and the potential utilization of the insect-associated intestinal microbiome in the future.

Endophytic fungus Penicillium steckii DF33 promoted tanshinones biosynthesis in Salvia miltiorrhiza by regulating the expression of CYP450 genes.

Salvia miltiorrhiza, a prominent traditional Chinese medicinal resource, has been extensively employed in the management of cardiovascular and cerebrovascular ailments. Ensuring the consistency of S. miltiorrhiza raw materials revolves around the imperative task of maintaining stable tanshinones content and composition. An effective approach in this regard involves the utilization of endophytic fungi as inducers. Within this context, our study spotlights an endophytic fungus, Penicillium steckii DF33, isolated from the roots of S. miltiorrhiza. Remarkably, this fungus has demonstrated a significant capacity to boost the biosynthesis and accumulation of tanshinones. The primary objective of this investigation is to elucidate the underlying regulatory mechanism by which DF33 enhances and regulates the biosynthesis and accumulation of tanshinones. This is achieved through its influence on the differential expression of crucial CYP450 genes within the S. miltiorrhiza hairy roots system. The results revealed that the DF33 elicitor not only promotes the growth of hairy roots but also enhances the accumulation of tanshinones. Notably, the content of cryptotanshinone was reached 1.6452 ± 0.0925 mg g-1, a fourfold increase compared to the control group. Our qRT-PCR results further demonstrate that the DF33 elicitor significantly up-regulates the expression of most key enzyme genes (GGPPS, CPS1, KSL1, CYP76AH1, CYP76AH3, CYP76AK1, CYP71D411) involved in the tanshinone biosynthesis pathway. This effect is particularly pronounced in certain critical CYP450 genes and Tanshinone ⅡA synthase (SmTⅡAS), with their expression levels peaking at 7 days or 14 days, respectively. In summary, endophytic P. steckii DF33 primarily enhances tanshinone biosynthesis by elevating the expression levels of pivotal enzyme genes associated with the modification and transformation stages within the tanshinone biosynthesis pathway. These findings underscore the potential of employing plant probiotics, specifically endophytic and root-associated microbes, to facilitate the biosynthesis and transformation of vital constituents in medicinal plants, and this approach holds promise for enhancing the quality of traditional Chinese medicinal materials.

Endophytic fungus Cladosporium tenuissimum DF11, an efficient inducer of tanshinone biosynthesis in Salvia miltiorrhiza roots.

Salvia miltiorrhiza is a traditional medicinal plant mainly used for cardiovascular and cerebrovascular disease treatment. Tanshinones are the main bioactive constituents of S. miltiorrhiza, which mainly accumulate around its root periderm tissue. Endophytic fungi are important bioelicitors or probiotics that can promote the accumulation of secondary metabolites and sustainable cultivation of medicinal plants. Among them, endophytic Cladosporium spp., possessing a variety of biotransformation and metabolic abilities, is an ideal elicitor source. Here, we used a gnotobiotic system to investigate the effects of the endophytic fungus Cladosporium tenuissimum DF11 on tanshinone biosynthesis in S. miltiorrhiza roots. The results showed that C. tenuissimum DF11 mainly colonizes the intercellular space of the root tissues and promotes tanshinone biosynthesis and accumulation in S. miltiorrhiza roots by upregulating the expression of the genes encoding for key enzymes HMGR, DXS, DXR, GGPPS, CPS, KSL and CYP76AH1 of the tanshinone biosynthesis pathway. The expression levels of almost all genes encoding for key enzymes reached the response peak in the first or second week after DF11 colonization. Taken together, the endophytic fungus C. tenuissimum DF11 could promote secondary metabolite accumulation in S. miltiorrhiza roots. These results indicate that DF11 will be a potential biofertilizer fungus to regulate and stabilize the quality of cultivated S. miltiorrhiza medicinal materials.