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 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.

Water conservation in fine roots can be important for the adaptation of trees to cold, nutrient-poor ecosystems. Although pressure-volume (p-v) curve traits are commonly used to assess leaf water conservation, little is known about their intraspecific variation in fine roots and their association with root functional traits, such as morphology and chemistry. Here, we aimed to determine the p-v curve traits of Betula ermanii and Abies mariesii fine roots at 2,000 and 2,500 m elevations and explore their intraspecific variation with root morphological and chemical traits in a subalpine forest. Turgor loss point (π_tlp), relative water content at π_tlp, osmotic potential at full hydration, and capacitance at full turgor (C_ft) were evaluated as p-v curve traits. Additionally, root diameter, specific root length, and root tissue density (RTD) were assessed as morphological traits, and nitrogen (N) content was measured as a chemical trait. For A mariesii roots, the C_ft was lower, and π_tlp was more negative at 2,500 m than at 2,000 m. The p-v curve traits of B ermanii roots remained unchanged with elevation. There were strong correlations between RTD and π_tlp and between N content and π_tlp and C_ft, especially for A. mariesii. These results indicated A. mariesii adjusted p-v curve traits with RTD and N content and achieved water conservation in fine roots at higher elevations. The p-v curve traits, particularly π_tlp and C_ft, reflected diverse tree strategies for environmental acclimation with fine-root carbon economy. Our findings highlighted the importance of adjusting water relation traits for acclimation to cold and nutrient-poor subalpine regions, particularly for evergreen coniferous species. The p-v curve traits revealed diverse fine-root water relation traits as a basis for water conservation capacity by preserving root function under stress conditions and enabling prolonged resource acquisition in a subalpine forest.

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.

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.

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.

The summer heat is a vital factor limiting the introduction of relatively large-leaf Rhododendron plants to low-altitude areas, making it crucial to evaluate the resistance of different germplasm to summer heat. A pot experiment was conducted in 2023 to investigate the temporal changes in the photosynthetic characteristics, physiological and biochemical characteristics, and chlorophyll fluorescence characteristics of 14 representative relatively large-leaf Rhododendron germplasm. The results showed the R. irroratum and 'Hotspur Red' exhibited the highest heat damage index (HDI), while R. jiulongshanense and 'Moser Maroon' had the lowest HDI among the 14 Rhododendron germplasm. The photosynthesis rate and F_v/F_m (maximum photochemical efficiency) initially decreased and then recovered in all germplasm except R. irroratum. In contrast, the leaf transpiration rate, stomatal conductance, and chlorophyll content gradually increased. Hydrogen peroxide concentration first decreased and then increased, while malondialdehyde concentration initially increased and then decreased. Additionally, the superoxide anion content gradually increased. The activities of superoxide dismutase, peroxidase, and catalase (CAT) initially increased and then decreased. The HDI was positively correlated with CAT activity (r = 0.28, P < 0.05) but negatively correlated with photosynthesis rate (r = -0.26, P < 0.05), leaf transpiration rate (r = -0.27, P < 0.05), and F_v/F_m (r = -0.43, P < 0.001). Variation in summer heat resistance, as indicated by HDI, was observed among the 14 Rhododendron germplasm. This heat resistance was mainly associated with leaf transpiration rate and F_v/F_m. The indirect role of antioxidant enzymes in maintaining reactive oxygen species homeostasis in summer heat resistance was observed. The results provide a reference for introducing and cultivating relatively large-leaf Rhododendron plants to low-altitude areas.

The physical filtering of pollinators is an important factor influencing pollination effectiveness. This study explored the potential functions of dense hairs that completely obstruct the entrance of floral tube in Marsdenia tinctoria by characterizing the flowers of this species, as well as its pollinators and their behavior. The corolla was white upon blooming in the morning, then turned yellow at night, and the flower finally dropped by the third morning. The hairs tended to be disheveled in yellow-petaled flowers. Pollination success increased with floral age. Direct observations of flowers in natural M. tinctoria populations over a period of 32 h recorded 126 visitors, of which 70% were wasps. We observed pollinia attached to the mouthparts of wasps, carpenter bees, and honeybees, but not to those of butterflies, moths, flies, or ants. Detailed examination of insect mouthparts and floral morphology indicated that insect visitors that acted as pollinators had mouthparts longer than the floral tubes, equipped with hairs to which pollinia could attach. The mouthparts of potter wasps were often covered with pollinaria, carrying on average 30-75 pollinia. The dense floral hairs were penetrated by large-bodied visitors, and blocked smaller visitors. Disturbance of these floral hairs allowed smaller insects to access nectar, suggesting that the hairs function in preventing nectar theft by smaller insects. This study presents the first case of wasp pollination in the genus Marsdenia and provides insights into the potential function of its dense floral hairs, a synapomorphy of this genus, in filtering floral visitors.

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.