Plant and Cell Physiology最新文献

NITRILASEs (NITs) are enzymes that have been identified across kingdoms. Nitrilases are industrially important hydrolases widely used in the production of valuable chemicals and medicines. In plants, nitrilases are phylogenetically divided into two groups: NIT1 and NIT4. The NIT1 (NIT1-3) subfamily detoxifying nitriles is specific to the Brassicaceae and catalyze the conversion of indole-3-acetonitrile (IAN), derived from indole glucosinolates (IGs) or indole-3-acetaldoxime (IAOx), into indole-3-acetic acid (IAA), the principal auxin, which provides an evolutionary advantage since it's a growth hormone. The NIT1 subfamily has been implicated in the catabolism of indole acetamide (IAM), although this has yet to be confirmed in planta. NIT4 appears to function in cyanide detoxification and exhibits strong specificity toward β-cyanoalanine. Additionally, it is hypothesized that NIT4, as well as enzymes of the NIT1 subfamily, might be involved in phenylacetic acid (PAA) formation from phenylacetonitrile/benzyl cyanide (PAN/BnCN). Crop plants, such as Zea mays and Oryza sativa, have been used to study NITs sporadically, consequently, our understanding of the role of nitrilases is primarily derived from studies of the model plant Arabidopsis thaliana, including single or sparse multiple mutants, reporter lines, or overexpressing lines. This review mainly focuses on the NIT1 subfamily, which plays a role in root and flower development. However, NITs expression and activity have primarily been demonstrated under plant stress conditions, biotic and abiotic stress, such as saline, drought, sulfate deficiency, thermomorphogenesis, during which NIT-dependent auxin biosynthesis is activated. In addition, the role of NITs has been confirmed in morphogenetic processes in in vitro cultures, highlighting their role in stress-induced developmental reprogramming.

Although microalgae such as diatoms and haptophytes have been studied to optimize fucoxanthin production, the complete biosynthetic pathway of fucoxanthin remains unclear. In this study, we subjected the haptophyte Tisochrysis lutea cells to heavy-ion beam irradiation to induce random mutations and obtained two greenish strains, GR1 and GR2, following exposures to 45 Gy and 100 Gy, respectively. The GR1 strain exhibited slow growth, whereas GR2 showed growth comparable to the wild-type strain. Neither GR1 nor GR2 accumulated fucoxanthin; instead, both strains accumulated fucoxanthin biosynthetic intermediates, haptoxanthin and phaneroxanthin, and harbored 74 and 148 mutation sites, respectively. As expected, higher radiation doses resulted in a greater number of mutations. Over 80% of these mutations consisted of short nucleotide insertions, primarily 4 to 8 bp in length. Additionally, mutations were identified in orthologs of the ZEP1 and CRTISO5 genes known in the diatom Phaeodactylum tricornutum to encode enzymes that convert haptoxanthin to phaneroxanthin and phaneroxanthin to fucoxanthin in GR1 and GR2 strains, respectively. The loss of fucoxanthin decreased photosynthetic capacity to some extent. However, the amounts of chlorophyll a and c did not change, suggesting that haptoxanthin and phaneroxanthin functioned as photosynthetic accessory pigments in the light-harvesting antennae. Because the genomic analysis results aligned with those from pigment analysis, our findings demonstrate that ZEP1 and CRTISO5 in T. lutea cells are involved in fucoxanthin biosynthesis and support the broader application of heavy-ion beam irradiation in fundamental microalgal research.

Parasitic flowering plants are often seen as keystone species due to the broad influence they exert on communities worldwide. Positive and negative effects associated with parasitic plant infestation have been documented for a variety of species in multiple locations and under different experimental conditions. However, the impact of the different drivers of climate change on these plants has only recently begun to be analyzed in more detail. In this context, most studies have dealt with modelling future distribution ranges of parasite species and assessing potential ecological impacts. Building on this work, this review discusses studies that have employed a more mechanistic approach to investigate different aspects of parasitic plant physiology under climate change. Considering results obtained for both hemi- and holo-parasites, I hypothesize that, in the presence of conditions that improve parasite performance, such as reduced intraspecific competition or increased diversity of host species, elevated levels of atmospheric CO2 can partially alleviate the negative impact of parasitism on host growth. However, this reduction of negative impacts is potentially hampered by other drivers of climate change, such as extreme high temperatures and severe drought events. Future research should strive to analyze the combined impact of different components of climate change simultaneously, preferably considering a wider diversity of parasitic plant species.

Mesquite (Prosopis laevigata, Fabaceae) is a legume widely distributed in Mexico, infested by the mistletoe Psittacanthus calyculatus, Loranthaceae) a parasitic plant that absorbs water and nutrients from the mesquite. For parasitism to become established, the mistletoe must evade host defenses. To date, these defenses have only been studied in hosts with advanced parasitic infestations, but the initial defense of mesquite against these infestations remains unknown. The objective of this work was to investigate the early stress responses of mesquite trees after the first physical contact during infection by P. calyculatus. To do so, we first artificially inoculated mistletoe seeds and placed them on mesquite branches to initiate the parasitism. Mistletoe inoculations induced the early production of the phytohormones salicylic acid and jasmonic acid. These changes were accompanied by higher cell wall invertase activity, which precedes the increase in sucrose, glucose, and fructose. H₂O₂ formation and superoxide dismutase and peroxidase activity were also induced, while catalase activity decreased. Analyses revealed the presence of phenolic compounds as a defensive response against the mistletoe and, finally, elevated phenylalanine ammonia lyase activity after mistletoe inoculation. These data suggest that host trees recognize the presence of parasitic plants and trigger immune signaling responses well before haustorium formation. This is the first step toward understanding the interaction between the host tree and the mistletoe at beginning of parasitism.

Obligate parasitic plants often establish symplastic connections with their hosts. This symplastic continuity is mediated by plasma membrane-lined channels referred to as interspecific secondary plasmodesmata, which develop at the interface between the parasite and its host. However, the molecular mechanisms underlying the formation of these interspecific secondary plasmodesmata remain unclear. In this mini review, we summarize current knowledge of plasmodesmata biogenesis at diverse cellular boundaries with distinct developmental origins, including those at graft junctions and between mesophyll and bundle sheath cells. Based on the literature review, we hypothesize that the formation of interspecific secondary plasmodesmata involves three key events: cell wall thinning, membrane rearrangement, and metabolic regulation. Finally, we discuss future research directions to elucidate the molecular basis of interspecific secondary plasmodesmata formation.

Phosphorus is an essential nutrient critical for plant growth and development, yet its availability in soil is often limited. Consequently, most land plants establish symbiotic relationships with arbuscular mycorrhizal fungi (AMF) to enhance phosphate uptake. Strigolactones (SLs) function as rhizosphere signaling molecules that promote AMF symbiosis, distinct from their role as phytohormones regulating various plant functions. We previously identified an SL in Marchantia paleacea and demonstrated that the SLs primarily serve as rhizosphere signals rather than phytohormones in M. paleacea due to the absence of cognate receptors. In this study, we investigate the spatial localization of SL biosynthesis and secretion in M. paleacea. We find that SL biosynthesis genes are predominantly expressed in the basal region of the thallus compared to the distal region. Using Citrine driven by the promoter of MpaCCD8B, an SL biosynthesis gene, we show expression in smooth rhizoids and the ventral epidermis adjacent to these rhizoids, under phosphate-deficient conditions. When plants are cultured on medium, fluorescence is also detected in parenchymal cells, where AMF colonization occurs. In soil conditions, AMF colonization enhances MpaCCD8B expression in parenchymal cells, where AMF colonize. Furthermore, we assess SL secretion through germination assay of root parasitic plant seeds, revealing that exudates from the basal and midrib region exhibit the highest activity. These findings underscore that SLs are synthesized in the basal ventral tissues of M. paleacea and secreted into the rhizosphere, facilitating effective communication with AMF.

Cannabis sativa L. (Cannabis) is a medicinal plant that produces and stores an abundance of therapeutic and psychoactive secondary metabolites, including phytocannabinoids and terpenes, in the glandular trichomes of its female flowers. We postulate that glandular trichome productivity has been under strong artificial selection in the pursuit for ever more potent cultivars. By comparing glandular trichomes of two modern cultivars and two traditional landraces, contrasting for cannabidiol and tetrahydrocannabinol contents, this study aims to identify drivers of enhanced phytocannabinoid productivity in improved drug cultivars. Fluorescent light microscopy, targeted metabolite analysis, and quantitative proteomics were used to examine differences in trichome morphology and metabolic activity. The increased concentrations of phytocannabinoids and terpenes of modern cannabis cultivars were reflected in larger trichomes that contained more secretory cells compared to traditional landraces. Proteomic analysis indicated that these modern trichome phenotypes were supported by increased metabolic activity, particularly in pathways related to energy production and lipid metabolism. Weighted Gene Co-expression Network Analysis suggested that histone H2A involved in DNA repair, regulator of fatty acid composition 3 involved in non-photosynthetic plastid development and olivetolic acid cyclase involved in phytocannabinoid biosynthesis are central hub proteins associated with high tetrahydrocannabinolic acid production. This study highlights the morphological and molecular differences observed between the specific modern and traditional Cannabis cultivars analysed in this study, offering valuable insights for enhancing phytocannabinoid production through targeted breeding and biotechnological approaches.

Strigolactones (SLs) are a class of plant hormones that play a crucial role in shaping plant architecture, significantly influencing plant adaptation to harsh environmental conditions. In this study, we examined the effects of a mutation in a component of the barley SL signalling pathway, the SL repressor HvDWARF53A, on plant growth and drought tolerance. We compared the results with those of a previously described barley mutant, which is highly tillered and drought-sensitive, carrying a mutation in the SL receptor gene HvDWARF14. The two mutants, hvd14.d and hvd53a.f, displayed contrasting phenotypes, including differences in plant height, tillering, and drought sensitivity. Under control conditions, ultrastructural analysis of hvd53a.f revealed smaller chloroplasts and fewer grana stacks, which may account for its reduced photosynthetic efficiency. Conversely, transcriptomic analysis linked the differentially expressed genes in hvd53a.f to antioxidation and stress responses, suggesting a potentially enhanced capacity to cope with drought. Further analysis revealed a strong connection between the SL signalling pathway and circadian clock components. Among these, CIRCADIAN CLOCK ASSOCIATED 1 emerged as a potential SL-responsive transcription factor (TF), possibly playing a key role in regulating tillering. Under drought conditions, hvd53a.f exhibited enhanced tolerance, as evidenced by higher relative water content, reduced chlorophyll degradation, and stable, albeit reduced, photosynthetic performance. Here, we identified the SL-related TF JUNGBRUNNEN 1 as a potential regulator of genes involved in water deficit response and antioxidation processes. Overall, the hvd53a.f mutation enhances drought tolerance while maintaining low, stable photosynthesis, highlighting HvD53A as a central node connecting SL signalling to stress resilience.

High-throughput sequencing has generated extensive omics data for Nicotiana species, a key model genus in the Solanaceae family. However, fragmented data and limited cross-species integration in current databases hinder the identification of disease-resistant genes and germplasm innovation. To address these challenges, we developed Nicotiana multi-dimensional omics database (http://biodb.com.cn/NMOD/index.html). This database systematically integrates whole-genome data from 23 tobacco varieties, 168 transcriptome datasets, 777 million variation sites, and phenotypic-agronomic data from 146 global germplasm accessions. Nicotiana multi-omics database (NMOD) emphasizes the annotation of 29 disease-resistant gene families across 10 representative varieties, performs differential expression analysis on transcriptomes under different disease resistance treatments and integrates tools for genomic visualization (JBrowse), homology searching (BLAST), and functional enrichment analysis. In summary, NMOD provides extensive insights into tobacco genomics and genetics, holding promise to enhance future research on disease resistance mechanisms and molecular breeding in tobacco.