Journal of Plant Research最新文献

The genus Acer belongs to the family Sapindaceae, whose representatives are characterized by a pentamerous perianth but typically possess only eight stamens. Such an androecium is believed to have evolved through the loss of two stamens. However, there is still no consensus on the origin of eight-staminate androecium including the positions of the two lost stamens and the pathway of their reduction compared to other Sapindaceae. We examined the early stages of flower development in five maple species belonging to different sections - four species with eight stamens and one species with ten stamens - using scanning electron microscopy. Measurements were performed to analyze the relative positions of stamen primordia, their size, and the floral meristem surface area. In addition, the perianth and androecium vasculature was studied to reveal petal-stamen complexes. We found that in three of four 8-staminate species, three stamens are initiated from common petal-stamen primordia, and five arise from single primordia. In A. tegmentosum Maxim., four stamens appear from common primordia with petals, and four from single primordia. Despite developmental differences, stamen distribution within the flower and the angles between adjacent stamens indicate a similar androecium construction in all species. In most species with eight stamens, the differences between two andoecial whorls have vanished. In contrast, A. nikoense (Miq.) Maxim., with ten stamens, possesses two distinct stamen whorls, the antepetalous stamens are initiated from common primordia. In the 8-staminate androecia of the genus Acer, the same two stamens have been lost as in other Sapindaceae. Within genus Acer, there is a certain decrease in the relative size of the floral meristem, accompanied by an increase in the number of common petal-stamen primordia and increased heterogeneity of the androecium (in A. tegmentosum) or reduction of some floral organs.

The commercially cultivated garlic varieties are infertile, leading to challenges in conventional hybrid breeding. Xinjiang garlic exhibits visually normal development of both androecium and gynoecium, but most pollen grains are not viable, thus allowing for the identification of flower development-related genes through combined morphological, anatomical, and cytological methods with transcriptome analysis. The inflorescence meristem differentiation of Xinjiang garlic plants was initiated after the 6th-7th leaves emerged, implying the transition from vegetative growth to reproductive growth. With the development of flower organs after bolting, normal pollen mother cell meiosis but no viable pollen grains were detected through triphenyl tetrazolium chloride (TTC) staining. Delayed tapetal degeneration, the gap between the tapetum and the middle layer, and degenerating and aborting anther are visible during anther development. There were 25 differentially expressed MYB genes and 64 flowering pathway related genes at different stages of flower development. The R2R3-MYB genes enriched in Module 22 are involved in the development of the tapetum and pollen. The co-expression network analysis showed that most MYB genes are related to flowering regulatory genes. The expression pattern of MYB35, MYB26, MYB80 and MMD1 may cause delayed degradation of the tapetum, or abnormal development of the pollen wall leading to pollen abortion.

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.