Journal of Experimental Botany最新文献

Cellulose is pivotal in regulating plant cell size and shape, and represents an abundant renewable resource for producing materials and chemicals. In seed plants, cellulose is synthesized at the plasma membrane by a hexameric protein complex synthesizing 18 glucose chains that bond together to form a microfibril; however, significant variation exists in the structure and physical properties of cellulose synthesized by other species and between different cell types. In this study, we surveyed the ability of 15 different catalytic subunits of the cellulose synthase complex (CESA proteins) derived from four species of charophycean green algae, a lycophyte, a bryophyte, and a fern to synthesize cellulose in the Arabidopsis secondary cell walls. Several CESA proteins can function in Arabidopsis in conjunction with endogenous CESA proteins in a pattern not easily predictable based on phylogenetics, demonstrating that heterologous expression is a valuable functional analysis tool. Additionally, two moss CESA proteins synthesized cellulose without Arabidopsis CESAs. The cellulose produced by the moss CESA proteins exhibited a much higher proportion of surface-exposed glucose residues but was sufficient to support normal plant growth. This study demonstrates that heterologous expression of CESA proteins generates cellulose with novel structures that offer a more suitable feedstock for biotechnological applications.

Experimental induction of polyploidy in turnip (Brassica rapa ssp. rapa) prior to 1980 led to the release of several tetraploid cultivars. Most experimentally induced polyploids are meiotically unstable and show reduced fertility, but we hypothesized that these commercially propagated turnip lines should have restored fertility and stabilized meiosis. Here, we collected all available B. rapa lines listed as tetraploid from germplasm banks, and investigated chromosome karyotypes, meiotic chromosome behaviour, and fertility. Unexpectedly, all accessions showed unstable meiosis: the mean tetravalent frequency per meiosis per plant ranged from 4.6 to 6.4 per line. Using chromosome-specific fluorescence in situ hybridization probes, we found that most chromosomes showed similar frequencies of tetravalent formation except for chromosomes A3 and A6, which predominantly formed tetravalents (>90%). Of the individuals sequenced (one per accession), approximately half (9 out of 21) were aneuploid (loss or gain of a whole chromosome), and two displayed additional chromosomal rearrangements. We nevertheless observed no significant phenotypic abnormalities or reductions in fertility, although all accessions were self-incompatible. Our findings indicate that stabilizing meiosis might not always be necessary to produce relatively fertile and homogeneous polyploid populations and point at self-incompatibility as a possible mechanism helping prevent fixation of undesirable aneuploid karyotypes.

Proline is a multifaceted amino acid in plants involved in both stress responses and development. Recent studies have shown that knockout mutants lacking pyrroline-5-carboxylate dehydrogenase (P5CDH), the enzyme responsible for the second step of proline catabolism, have impaired nitrogen remobilization and carbon allocation to seeds. Here, we demonstrate that seed development is also significantly impaired in p5cdh mutants, particularly during the transition between embryogenesis and maturation. Specifically, the p5cdh mutation leads to an arrest in embryo elongation and a reprogramming of seed metabolism during maturation, resulting in reduced accumulation of storage compounds and compromised acquisition of dehydration tolerance. These effects are further exacerbated under high-nitrate conditions. Together, our findings highlight a crucial role for proline catabolism in supporting the ability of maturing embryos to utilize glutamine as a nitrogen source, particularly in response to nitrogen availability.

Nitrogen is the pivotal macronutrient for grain protein synthesis, which is important in human nutrition and the establishment of derived products. However, nitrogen metabolism in plants is likely to be susceptible to abiotic factors such as those derived from climate change: drought, elevated [CO2], and temperature. How the triple interaction of these factors will affect nitrogen metabolism and grain quality of cereals is unknown. This study aimed to determine the response of nitrogen metabolism in barley-one of the temperate cereals most tolerant to abiotic stresses-to the triple interaction during its whole life span. Our results pointed out a growth stage-dependent response on final nitrogen status. At the vegetative stage, the nitrogen assimilation capacity was boosted and matched with the biomass gain without altering the nitrogen status. However, at the anthesis and maturity stages, the nitrogen status of plants and grains was reduced. A non-overlapping effect of biomass dilution and lower mass flow is highlighted, while lower photorespiration activity cannot be completely ruled out. The elevated [CO2] is the main driver regulating nitrogen metabolism at the physiological level under future drought conditions, whereas elevated temperature hampers grain formation.

Pollinators share the complex information and resource landscape of their host plants with herbivores. Yet, how sap feeders affect floral attractiveness to pollinators remains poorly understood, despite the critical role of this tripartite interaction in natural and agricultural ecosystems. In dioecious plant species, which display pronounced sexual dimorphism, these intricate interactions may vary in magnitude and direction between females and males, with significant implications for plant population dynamics and species co-evolution. In this study, we examined how infestation by the oligophagous aphid Brachycaudus lychnidis affects sex-specific interactions between the dioecious plant Silene latifolia and its specialist moth pollinator Hadena bicruris. We exposed male and female plants to aphid herbivory and evaluated its effects on floral traits (visual cues, floral scent, and nectar chemistry) and pollinator behaviour. While aphid infestation affected some floral traits equally in both sexes and others more strongly in males or in females, we observed stronger declines in female attractiveness to pollinators, which were mainly linked to nectar compounds potentially acting as feeding cues or behavioural modulators. We discuss our results in the light of sexual selection and plant defence theory while emphasizing the complementarity of female and male traits in stabilizing this specialized plant-pollinator-herbivore system.

Switchgrass (Panicum virgatum) is a promising bioenergy crop due in part to its resilience to drought stress. However, the significance of drought timing remains poorly understood, both from a plant biology perspective and in terms of its impact on downstream biofuel production. This study determines the developmental stage-specific physiological and metabolic responses of switchgrass to drought stress and their implications for biofuel production using a custom-built programmable irrigation system. Vegetative-, flowering-, and senescence-stage drought significantly reduced carbon dioxide assimilation and stomatal conductance without affecting biomass yield. Metabolic profiling revealed significant accumulation of glucose, fructose, quinic acid, shikimate, and γ-aminobutyric acid (GABA) during vegetative-stage drought, while flowering and senescence stages exhibited limited metabolic changes. Similarly, specialized metabolites also displayed distinct developmental patterns, with vegetative-stage drought driving the most pronounced metabolic alterations. Thermochemically treated and hydrolyzed switchgrass biomass from vegetative-stage drought showed elevated lignocellulose-derived compounds and saponins, with the latter most positively correlating with fermentation lag times. Conversely, senescence-stage drought enhanced ethanol yields while lowering saponin levels in the hydrolysates. While vegetative-stage drought enhanced physiological resilience, it compromises downstream biofuel production by introducing fermentation inhibitors, particularly saponins.

Starch initiation has been intensively investigated, and in tubers of Solanum tuberosum it is controlled by a heteromultimeric isoamylase (ISA) complex composed of ISA1 and ISA2. In Arabidopsis, two non-catalytic starch binding proteins regulate leaf starch metabolism, namely EARLY STARVATION 1 (ESV1) and LIKE EARLY STARVATION 1 (LESV). These proteins both interact with starch glucans through a C-terminal antiparallel β-sheet domain and differ by the presence of a 115 amino acid N-terminal overhang in LESV. Here, we used CRIPSR/Cas9 to inactivate LESV or ESV1 in potato and characterized the resulting tuber starches. Starch from esv1 mutants was unaffected whereas granule diameter was severely reduced in tubers of lesv plants. This was negatively correlated with the number of granules, consistent with an altered starch-initiation phenotype. Strikingly, SEM of purified starches revealed that lesv plants phenocopy isa1 and isa2 antisense lines described 20 years ago. Using yeast two-hybrid assays, we confirmed that LESV interacts with ISA1 in potato, as previously demonstrated in rice, providing molecular evidence for their functional association in potato. This interaction supports the hypothesis that LESV acts in concert with the ISA1/ISA2 complex, probably regulating the early steps of glucan organization required for proper starch granule formation.

Using the optical vulnerability method, we evaluated leaf and stem embolism resistance across three Populus species (P. trichocarpa, P. deltoides, and P. grandidentata) grown under field and glasshouse conditions to explore the mechanisms of vulnerability segmentation between organs. Classical vulnerability segmentation occurs when leaf xylem is more vulnerable to embolism than stem xylem, with leaves serving as hydraulic 'fuses' that protect the hydraulic integrity of the stem during drought. Recent evidence suggests that reverse vulnerability segmentation-when leaves have higher embolism resistance than stems-may occur in Populus species. We observed reverse segmentation exclusively in field-grown older stems, while no segmentation was found in glasshouse-grown or newly formed stems. X-ray micro-computed tomography and hydraulic measurements confirmed that the more vulnerable field-grown older stems had significant native embolism (>25% loss of conductivity). These findings support the hypothesis that reverse segmentation arises not from inherent xylem properties, but from the accumulation of native embolism, probably induced by winter freeze-thaw cycles or stem age. Our results provide a mechanistic explanation for reverse segmentation and suggest that its occurrence in Populus may be a byproduct of environment and life history rather than an adaptive trait of xylem architecture.

The effects of climate change are highly disruptive for reliable and sustainable crop production as crops have been regionally adapted to respond favorably to a set of regular, combined environmental cues. Notably in wheat, the most widely cultivated crop, the timing of floral meristem transitions and flowering is largely regulated by the combination of photoperiod and temperature cues. Identifying and understanding the key genes which regulate the physiological responses to these combined environmental cues has been important to enable the optimal development of cultivars. Winter grown crops are important as they provide ground cover, high biomass and high yield potential. However, they are critically sensitive to the duration and level of cold season temperatures and the onset of the lengthening spring photoperiod. Therefore, to enable climate robust cultivars we need to understand and tailor the crops response to the winter environment, being resilient enough to survive but flexible enough not to require a standard winter each year. Here we detail the challenges and opportunities which are presented by the changing environmental conditions for the adaptation of winter wheat.