Journal of Plant Research最新文献

Cuticular waxes are a complex mixture of long-chain aliphatic compounds, including alkanes, aldehydes, alcohols, ketones, and esters, that cover the outer surface of most terrestrial plants. While cuticular waxes play a pivotal role in plant adaptation to various environmental stresses, the specific roles of individual molecular species, particularly wax esters (WEs), remain poorly understood. In this study, we investigate the evolution and function of wax ester biosynthesis in land plants, focusing on the WSD (wax synthase/DGAT) enzyme family. We demonstrate that the ancestral origin of WSD enzymes traces back to streptophyte algae, specifically Klebsormidium nitens (KnWSD1). Our findings provide evidence that KnWSD1 functions as a monofunctional WSD catalyzing WE formation without producing triacylglycerols (TAGs). By generating Arabidopsis mutants with multiple WSD gene knockouts, we uncover a crucial role for WEs in supporting floral organ development under high humidity. Our results reveal that WEs are essential for floral organ development and provide new insights into their evolutionary significance in plant adaptation to terrestrial environments.

The species-rich legume family displays diverse mechanisms for pollen presentation and release, including brush, piston, valvular, and explosive types, influenced by variations in floral architecture. Among papilionoids, a group characterized by flag-flowers, early-branching species often deviate from this typical pattern. This study investigates Myroxylon peruiferum L.f., an early-branching papilionoid legume native to the Brazilian Atlantic Forest, with non-papilionaceous flowers. Through detailed macromorphological, anatomical, histochemical, and ultrastructural analyses of floral organs, we reveal new insights into pollen release and presentation mechanisms in legumes. Pollen is released through an unusual process: the anther opens via an apical wide slit that gradually extends toward the base, releasing pollen in stages. Ducts in the sepals, petals, ovary, and anther secrete translucent oleoresin droplets that harden when released into the external environment. These serve multiple functions, including enhancing flower visibility, facilitating secondary pollen presentation by attaching pollen to the anther apex and petal tips, and acting as olfactory attractants due to their terpene content. M. peruiferum presents several unique traits not previously described in this subclade, including (a) oleoresin overflow through anther pores, (b) uncommon rimose anther dehiscence, and (c) a novel form of secondary pollen presentation via oleoresin drops. These findings provide important new insights into the reproductive strategy of this species and offer broader implications for legume biology.

Trichoderma spp., as excellent biocontrol agents, can induce systemic resistance to protect plants from phytopathogen attacks. In a previous study, Trichoderma biofertilizer activated the MsERF105 transcription factor (TF), which further enhanced the resistance of Malus sieversii against Alternaria alternata f. sp. mali, but how resistance signals are transmitted is still unknown. In this study, it was found that the MsERF105-centered disease-resistant regulatory network was induced by Trichoderma in M. sieversii. The TF-centered yeast one-hybrid indicated that WRKY33 and WRKY40 bound to WBOXATNPR1 elements and GT1 bound to GT1CONSENSUS elements in the promoter of MsERF105 to activate its expression. In addition, the proteins that interacted with MsERF105 were identified by yeast two-hybrid, including FUBP2 and HSP17.8. Furthermore, the candidate target genes of MsERF105 were screened using RNA-Seq, and yeast one-hybrid and tobacco transient transformation further showed MsERF105 bound to GCCBOX elements to regulate the expression of bHLH162, ERF017, NAC83 and NAC104; bound to CCAATBOX elements to regulate the expression of HSFs, HSP70s and HSP20; and bound to ERS elements to regulate the expression of DRPs. Finally, the Trichoderma-induced MsERF105-centered regulatory network of M. sieversii against A. alternata f. sp. mali was built, which provided reliable theoretical guidance for the application of Trichoderma and the disease-resistance breeding of M. sieversii.

Rice is a staple food for over half of the world's population. To feed the growing population, molecular breeders aim to increase grain yield. Grain size is an important factor for crop productivity, and it has been extensively studied. However, molecular breeders face a major challenge in further improving crop productivity in terms of grain yield and quality. Grain size is a complex trait controlled by multiple genes. Over the past few decades, genetic studies have identified various gene families involved in grain size development. The list of molecular mechanisms, and key regulators involved in grain size development is constantly expanding, making it difficult to understand the main regulators that play crucial roles in grain development. In this review, we focus on the major regulators of grain size, including G-protein signaling, the mitogen-activated protein kinase (MAPK) pathway, transcriptional regulation, the ubiquitin-proteasome degradation (UPD) pathway, and phytohormone signaling. These molecular mechanisms directly or indirectly regulate grain size. We provided a comprehensive understanding of the genes involved in these mechanisms and cross discussions about how these mechanisms are interlinked. This review serves as a valuable resource for understanding the molecular mechanisms that govern grain development and can aid in the development of molecular breeding strategies.

The adaptation of plants to environmental conditions involves a transcriptional response. "Field transcriptomics" is an emerging concept for studying plants in their natural habitat. However, this term includes studies in which cold storage was possible until further processing in a laboratory. Previous studies proposing onsite RNA extraction methods are limited to descriptions of RNA purity, quantity, and quality, and lack a thorough evaluation of transcriptome quality, and transcriptomic evaluations of RNA storage solutions in plants are, to our knowledge, only available for periods of less than a day. This issue is critical for studying plants in geographically difficult-to-access regions, where keeping the cold chain is unrealistic. In this study, the transcriptome of the non-model plant Helonias orientalis (order: Liliales) was evaluated before and after storage of the leaf tissue for one and fourteen days at 25 °C in RNAlater and TRIzol, respectively. Additionally, field-friendly protocols were similarly evaluated for onsite plant RNA extraction at ambient temperature with lightweight equipment that can run on a portable generator, including a guanidine isothiocyanate-free protocol that is compatible with the polyphenol-rich wild strawberry Fragaria vesca. The quality of the transcriptome assembly after 1-day storage and our optimized onsite methods had similar results to that of the state-of-the-art. However, in terms of differential expression analysis, onsite extraction methods performed better overall than the stored tissue samples. We expect that our onsite RNA extraction methods will provide valuable insights into the transcriptional regulation of plants in areas where research equipment is difficult to access.

Plants generate electrical signals in response to mild and severe environmental stimuli to transmit physiological information and ultimately trigger defensive responses during stressful events. It has been proposed that detecting and characterizing such signals could allow researchers to mimic specific electrical stimuli and provoke desirable responses in crops. Nevertheless, manually inserting electrodes in plant tissues leads to irregular data records due to a lack of uniformity across insertion events. For this reason, we manufactured a prototype of an electrode/needle insertion device built in aluminum and acrylic and used it to measure electrical signals in C. annuum plants. As a result, the device had more consistent insertion characteristics such as depth and alignment between electrodes and with plant stems. The device was also used to obtain electrical signals and compare them with the signals obtained using the traditional insertion technique, demonstrating that the use of the device promotes stability and repeatability in the captured signals.

Numerous studies have examined the reproductive systems of threatened orchids to develop effective conservation strategies. However, the detrimental effects of seed predators on seed production are often overlooked. In this study, we evaluated the impact of the seed-parasitic fly Japanagromyza tokunagai on the seed production of the endangered orchid Cephalanthera falcata, based on observations from five locations over one year and from a single location over four years in Chiba Prefecture, Japan. Our findings showed that J. tokunagai caused 100% capsule damage across all sites and years examined. Although some infested fruits still produced seeds in certain locations and years, the quantities were very low. Consequently, we observed a 99.1-100% reduction in seed production across all populations investigated. These results suggest that reduced seed production could limit generational turnover, potentially threatening the reproductive success and long-term survival of C. falcata, at least in the populations studied. This highlights the need to mitigate the negative impact of J. tokunagai on seed production in C. falcata. Combining artificial pollination with the bagging of individual inflorescences could be an effective approach, capable of increasing seed production by more than 100-fold. Given the fungal dependence and low germination rates of C. falcata, future work should also examine seedling recruitment to better understand the impacts of seed loss and improve estimates of long-term resilience.

Crassulacean acid metabolism (CAM), a specialized mode of photosynthetic carbon assimilation characterized by nocturnal fixation of atmospheric CO₂ and vacuolar malic acid storage, is found in a wide variety of vascular plant species, mainly those inhabiting water-limited environments. Identifying and characterizing diverse CAM species enhances our understanding of the physiological, ecological, and evolutionary significance of CAM photosynthesis. In this study, we examined the effect of CO₂ elimination on chlorophyll fluorescence-based photosynthetic parameters in two constitutive CAM Kalanchoe species and six orchids. In CAM-performing Kalanchoe species, the effective quantum yield of photosystem II showed no change in response to CO₂ elimination during the daytime but decreased with CO₂ elimination at dusk. We applied this method to reveal the photosynthetic mode of epiphytic orchids and found that Gastrochilus japonicus, Oberonia japonica, and Bulbophyllum inconspicuum, but not B. drymoglossum, are constitutive CAM plants, which were also confirmed by malate determination. Our data propose a novel approach to identify and characterize CAM plants without labor-intensive experimental procedures. Although B. drymoglossum leaves had relatively high malate content, they did not depend on it to perform photosynthesis even under water-deficient or increased light conditions. Anatomical comparisons revealed a notable difference in leaf structure between B. drymoglossum and B. inconspicuum; B. drymoglossum leaves possess large water storage tissue internally, unlike B. inconspicuum leaves, which develop pseudobulbs. Our findings suggest different evolutionary adaptations to water deficit between closely related B. drymoglossum and B. inconspicuum.

Salinity and light markedly influence cyanobacterial viability. High salinity disrupts the osmotic balance, while excess light energy affects redox potential in the cells. Regulating the ratio of saturated and unsaturated alka(e)ne and fatty acids in cyanobacteria is thought to have crucial roles in coping with these stresses by regulating membrane fluidity. In Synechococcus elongatus PCC 7942 (Syn7942), alkane is produced from fatty acid metabolites using acyl-acyl carrier protein reductase (Aar) and aldehyde-deformylating oxygenase (Ado) enzymes. However, the role of alka(e)nes and their correlation with fatty acid-related compounds, especially under salinity stress, is not yet fully understood. This study explored the significance of the natural alka(e)ne biosynthesis pathway using Syn7942. The role of alka(e)ne was assessed using single and double knockout mutants of the aar and/or ado genes in this biosynthetic process. The alka(e)ne levels and membrane lipid content exhibited an inverse relationship, correlating with cell fluidity under high-salinity and high-light conditions. The absence of alka(e)ne resulted in a severe growth phenotype of Δado and Δaar/Δado under high-salinity conditions and less severe under high-light conditions. In addition, feeding with C15:0 and/or C17:0 alkanes complemented the growth phenotype with different accumulation profiles. The Δaar mutant exhibited higher resistance to high salinity than the Syn7942 WT, indicating the importance of Ado for survival at high salinity. Overall, lipid-related compounds, especially alka(e)nes, markedly contribute to cell integrity maintenance under high-salinity conditions by regulating membrane rigidity and fluidity.

Sasa senanensis (a dwarf bamboo), an evergreen herbaceous plant native to the cool temperate regions of eastern Asia, endures seasonal temperature fluctuations and significant variations in light intensity typical for understory plants. Following snowmelt in early spring, the light intensity received by Sasa leaves surges, then diminishes as the canopy of upper deciduous trees develops. The current-year leaves of S. senanensis unfold under these shaded conditions, rendering the preservation of overwintering leaves vital for maintaining photosynthetic productivity in early spring. This study investigated the adaptations of overwintering leaves of S. senanensis to the low temperatures and elevated light conditions typical of early spring, examining whether these leaves dissipate absorbed light energy as heat and/or reduce their antenna size in response to increased light levels. Comprehensive analyses of Fv/Fm and photosynthetic pigment compositions were conducted throughout the spring to autumn seasons from 2014 to 2017. Our results indicate that Fv/Fm in overwintering leaves was initially low in early spring but increased gradually before the onset of shading, maintaining high levels under shaded conditions across all examined years. The chlorophyll a/b ratio increased post-snowmelt and decreased with intensified shading annually, with the exception of 2015, suggesting that reductions in antenna size are not essential for Fv/Fm recovery. Furthermore, the quantities and de-epoxidation state of xanthophyll cycle pigments increased after snowmelt despite rising temperatures, then decreased with progressive shading each year, indicating that overwintering leaves adapt to early spring conditions by modulating their xanthophyll cycle pigments. This study demonstrates that the overwintering leaves of S. senanensis exhibit a flexible response in photosystem pigments to variations in the light environment.