Journal of Experimental Botany最新文献

Elevated atmospheric CO2 (e[CO2]) often enhances plant photosynthesis and improves water status. However, the effects of e[CO2] vary significantly and are believed to be influenced by water availability. With the future warmer climate expected to increase the frequency and severity of extreme rainfall, the response of plants to e[CO2] under changing precipitation patterns remains uncertain. We examined the effects of e[CO2] and different irrigation regimes on perennial ryegrass in a Free-Air CO2 Enrichment (FACE) experiment. Immediately after irrigation, the mean net photosynthetic rate was 21.2% higher under e[CO2] compared to ambient conditions. This benefit increased over time, reaching 31.3% higher as days since watering increased, indicating a substantial increase in photosynthetic benefit with longer intervals between watering. Mean stomatal conductance was 21% lower in ryegrass under e[CO2] immediately after irrigation compared to ambient plots. However, the reduction in stomatal conductance under e[CO2] decreased as the interval between irrigation events increased, showing no difference 7-10 days after an irrigation event. These results imply that plants benefit most from carbon fertilisation, assimilating relatively more carbon and losing less water, during periods with less frequent rainfall. These findings have significant implications for understanding leaf-level responses to climate change.

Paclitaxel (PTX) is a high value plant natural product derived from Taxus (yew) species. This plant specialized metabolite (PSM) and its derivatives constitute a cornerstone for the treatment of an increasing variety of cancers. New applications for PTX also continue to emerge, further promoting demand for this WHO-designated essential medicine. Here we review recent advances in our understanding of PTX biosynthesis and its cognate regulation, which have been enabled by the development of transcriptomic approaches and the recent sequencing and annotation of three Taxus genomes. Collectively, this has resulted in the elucidation of two functional gene sets for PTX biosynthesis, unlocking new potential for the use of heterologous hosts to produce PTX. Knowledge of the PTX pathway also provides a valuable resource for understanding the regulation of this key PSM. Epigenetic regulation of PSM in plant cell culture is a major concern for PTX production, given the loss of PSM production in long-term cell cultures. Recent developments aim to design tools for manipulating epigenetic regulation, potentially providing a means to reverse the silencing of PSM caused by DNA methylation. Exciting times clearly lie ahead for our understanding of this key PSM and improving its production potential.

Medicinal plants are valued for their contributions to human health. However, the growing demand for medicinal plants and the concerns regarding their quality and sustainability have prompted the reassessment of conventional production practices. Controlled-environment cropping systems, such as vertical farms, offer a transformative approach to production of medicinal plants. By enabling precise control over environmental factors, such as light, carbon dioxide, temperature, humidity, nutrients, and airflow, controlled environments can improve the consistency, concentration, and yield of bioactive phytochemicals in medicinal plants. This review explores the potential of controlled-environment systems for enhancing production of medicinal plants. First, we describe how controlled environments can overcome the limitations of conventional production in improving the quality of medicinal plants. Next, we propose strategies based on plant physiology to manipulate environmental conditions for enhancing the levels of bioactive compounds in plants. These strategies include improving photosynthetic carbon assimilation, light spectrum signalling, purposeful stress elicitation, and chronoculture. We describe the underlying mechanisms and practical applications of these strategies. Finally, we highlight the major knowledge gaps and challenges that limit the application of controlled environments, and discuss future research directions.

Cannabis sativa L. is one of the oldest domesticated crops. Hemp-type cultivars, which predominantly produce non-intoxicating cannabidiol (CBD), have been selected for their fast growth, seed, and fibre production, while drug-type chemovars were bred for high accumulation of tetrahydrocannabinol (THC). We investigated how the generation of CBD-dominant chemovars by introgression of hemp- into drug-type Cannabis impacted plant performance. The THC-dominant chemovar showed superior sink strength, higher flower biomass, and demand-driven control of nutrient uptake. By contrast, the CBD-dominant chemovar hyperaccumulated phosphate in sink organs leading to reduced carbon and nitrogen assimilation in leaves, which limited flower biomass and cannabinoid yield. RNA-seq analyses determined organ- and chemovar-specific differences in expression of genes associated with nitrate and phosphate homeostasis as well as growth-regulating transcription factors that were correlated with measured traits. Among these were genes positively selected for during Cannabis domestication encoding an inhibitor of the phosphate starvation response, SPX DOMAIN GENE3, nitrate reductase, and two nitrate transporters. Altered nutrient sensing, acquisition, or distribution are likely a consequence of adaption to growth on marginal, low-nutrient-input lands in hemp. Our data provide evidence that such ancestral traits may become detrimental for female flower development and consequently overall CBD yield in protected cropping environments.

Cannabis sativa L., one of the oldest cultivated crops, has a complex domestication history due to its diverse uses for fibre, seed, oil, and drugs, and its wide geographic distribution. This review explores how human selection has shaped the biology of hemp and drug-type Cannabis, focusing on acquisition and utilization of nitrogen and phosphorus, and how resulting changes in source-sink relations shape their contrasting phenology. Hemp has been optimized for rapid, slender growth and nutrient efficiency, whereas drug-type cultivars have been selected for compact growth with large phytocannabinoid-producing female inflorescences. Understanding these nutrient use and ontogenetic differences will enhance our general understanding of resource allocation in plants. Knowledge gained in comparison with other model species, such as tomato, rice, or Arabidopsis can help inform crop improvement and sustainability in the cannabis industry.

Cannabis sativa L. is an ancient crop, but its agricultural adoption has been interrupted to prevent the use of marijuana as a psychoactive drug. Nevertheless, hemp-the C. sativa type with low concentrations of intoxicating Δ9-tetrahydrocannabinoid-is experiencing a resurgence in interest due to loosened cultivation restrictions and its potential as a multipurpose bio-based crop. Hemp has valuable applications, including production of medicines from its non-intoxicating cannabinoids, food, medical, and industrial uses of its seed oil rich in polyunsaturated fatty acids, and production of fibers for textiles and industry from its stems. Recently, several hemp genomic and genetic resources have been developed, allowing significant expansion of our knowledge of major hemp traits, such as synthesis of cannabinoids, oil, and fibers, and regulation of flowering and sex determination. Still, hemp is an underimproved crop, and its development will depend on the ability to expand and collectively use the novel resources arising from fast advancements in bioinformatics and plant phenotyping. This review discusses current genetic and genomic knowledge of the most important hemp traits, and provides a perspective on how to further expand such knowledge and tackle hemp improvement with the most up-to-date tools for plant and hemp research.

Opium poppy is a crop of great commercial value as a source of several opium alkaloids for the pharmaceutical industries including morphine, codeine, thebaine, noscapine, and papaverine. Most enzymes involved in benzylisoquinoline alkaloid (BIA) biosynthesis in opium poppy have been functionally characterized, and opium poppy currently serves as a model system to study BIA metabolism in plants. BIA biosynthesis in opium poppy involves two biosynthetic gene clusters associated respectively with the morphine and noscapine branches. Recent reports have shown that genes in the same cluster are co-expressed, suggesting they might also be co-regulated. However, the transcriptional regulation of opium poppy BIA biosynthesis is not well studied. Opium poppy BIA biosynthesis involves three cell types associated with the phloem system: companion cells, sieve elements, and laticifers. The transcripts and enzymes associated with BIA biosynthesis are distributed across cell types, requiring the translocation of key enzymes and pathway intermediates between cell types. Together, these suggest that the regulation of BIA biosynthesis in opium poppy is multilayered and complex, involving biochemical, genomic, and physiological mechanisms. In this review, we highlight recent advances in genome sequencing and single cell and spatial transcriptomics with a focus on how these efforts can improve our understanding of the genomic and cell-specific regulation of BIA biosynthesis. Such knowledge is vital for opium poppy genetic improvement and metabolic engineering efforts targeting the modulation of alkaloid yield and composition.

Dioecy in flowering plants has evolved independently many times, and thus the genetic mechanisms underlying sex determination are diverse. In hemp (Cannabis sativa), sex is controlled by a pair of sex chromosomes (XX for females and XY for males). In an attempt to understand the molecular mechanism responsible for sex expression in hemp plants, we carried out RNA sequencing of male and female plants at different developmental stages. Using a pipeline involving differential gene expression analysis and weighted gene co-expression network analysis, we identified genes important for male and female flower development. We also demonstrate that sex-biased expression is already established at very early vegetative stages, before the onset of reproductive development, and identify several genes encoding transcription factors of the REM, bZIP, and MADS families as candidate sex-determination genes in hemp. Our findings demonstrate that the gene regulatory networks governing male and female development in hemp diverge at a very early stage, leading to profound morphological differences between male and female hemp plants.