Journal of Plant Research最新文献

Different light intensities in cerrado stricto sensu (CSS) and semideciduous seasonal forests (SSF) can result in distinct morphological responses among woody species. This research evaluated the size and bud composition, budbreak time, and crown architecture of woody species in response to precipitation and varying light intensities in these two environments. The study was conducted in CSS (19°57'29″ S and 44°25'29″ W) and an SSF fragment (19°53'84″ S and 44°25'56″ W) in Minas Gerais, Brazil. The research focused on four species: Miconia albicans and Xylopia aromatica, which occur in both environments, as well as Bauhinia cfr. ungulata (CSS) and B. cfr. rufa (SSF). Shoots from the main axis were manually dissected, and budbreak times were recorded. Crown architecture was evaluated based on diagrams of the vegetative above-ground structure, excluding leaves. Light intensities was measured with a luxmeter at the crown's apex, interior, and base. Shoots were larger and had more preformed organs in CSS than in SSF trees. Trichomes were observed on shoots of all CSS and SSF trees. The number of cataphylls varied: B. cfr. ungulata had one, B. cfr. rufa had 1-3, while compound buds of X. aromatica averaged 5.4 in CSS and 3.7 in SSF. Simple buds of X. aromatica and all M. albicans buds lacked cataphylls. Budbreak occurred in September for M. albicans (CSS and SSF), October for B. cfr. ungulata, Juy-October for X. aromatica and August-October for B. cfr. rufa. A positive correlation between budbreak and rainfall was recorded only for B. cfr. ungulata. Despite differences in bud size and composition between environment, these didn't result in distinct crown architectures. The findings highlight that tropical woody species with cataphyll-protected buds are as common as in temperate regions. Further research is needed to explore phylogenetic traits and the ecological role of cataphylls in tropical species.

The transition of plants in the green lineage from aquatic to terrestrial environments during the bryophyte stage marked a pivotal point in evolution. Successful terrestrialization required evolutionary adaptations to harsh and fluctuating light conditions, where direct irradiation is stronger than in aquatic environments. To cope with these challenges, plants evolved regulatory mechanisms to control cellular activities. One such acclimation is rapidly reversible, energy-dependent non-photochemical quenching (NPQ), which dissipates excess light energy as heat to protect the photosynthetic apparatus. Another critical innovation is abscisic acid (ABA) signaling, believed to have first emerged in bryophytes. Here, we reveal a potential link between these two key acclimations in bryophytes. We demonstrate that exogenous ABA induces NPQ in the moss Physcomitrium patens, increasing the levels of LHCSR, a key NPQ regulator, while concurrently decreasing PsbS. Exogenous ABA also enhances the xanthophyll cycle pigments, contributing to NPQ. In mutants deficient in ABA signaling components, including SNF1-related kinase 2 (SnRK2) and the transcription factor, Abscisic Acid-Insensitive 3 (ABI3), ABA-induced NPQ, LHCSR and PsbS expression, and xanthophyll cycle pigment accumulation were significantly reduced. These findings suggest that exogenous ABA enhances NPQ through the SnRK2 and ABI3-mediated signaling pathway by promoting LHCSR expression and xanthophyll cycle pigment production. We propose that the integration of ABA signaling and NPQ represent a critical evolutionary milestone, enabling early land plants to adapt and thrive in terrestrial environments.

Although Tetracentron (Trochodendraceae) is endemic to eastern Asia today, the fossil record indicates that it was formerly more widespread across the northern hemisphere. Infructescences from the Paleocene of Wyoming, USA, documented herein, represent the oldest known occurrence of the genus. Details of the morphology, including spikes of sessile, tetracarpellate, apically dehiscent capsules with styles emerging from the lower part of the fruit, and a nectary bulge beneath each style, are revealed by micro-CT scanning of specimens preserved as molds and casts in siltstone. The discovery of Tetracentron linchensis sp. nov. indicates that Tetracentron and Trochodendron had already diverged by about 60 million years ago and were sympatric, along with the extinct relative, Eotrochion, in the Paleocene of Wyoming. North American fossil occurrences of Trochodendraceae, including extinct Eocene and Miocene genera, as well as both extant genera, highlight a former diversity and geographic spread that is no longer evident in the surviving Asian Trochodendraceae.

Living organisms are constantly at the risk of DNA damage caused by factors such as DNA replication errors, reactive oxygen species, and UV radiation. In plants, DNA damage activates the NAC-type transcription factor SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) that governs DNA damage responses such as cell cycle arrest, stem cell death, and early onset of endoreplication. However, molecular mechanisms underlying the early induction of endoreplication onset in response to DNA damage remain elusive. In this study, we show that CELL CYCLE SWITCH 52 A1 (CCS52A1), an activator of the APC/C E3 ligase, plays a major role in the early onset of endoreplication in response to DNA double-strand breaks (DSBs) in Arabidopsis roots. Upon DSBs, SOG1 directly binds to the CCS52A1 locus, thereby inducing its expression. Moreover, early transition to endoreplication in response to DSBs is suppressed in ccs52a1 knockout roots. Our data propose that increased polyploidy may function as a unique adaptative mechanism to genotoxic stress in plants.

Aeluropus lagopoides is salt secreting halophytic perennial grass that commonly grows in coastal regions. Under excessive saline conditions, A. lagopoides is able to thrive and completes its life cycle. It has developed various adaptive mechanisms to tolerate harsh environmental conditions. Aeluropus follow the novel mechanism of salt secretion by excreting Na⁺ from the leaf sheath and stem of the plant in the form of salt crystals. Various salt responsive genes and transcription factors have been studied under salinity stress in A. lagopoides. Economically important phytochemicals are also present in this plant, thus, making it industrially important. Utilization of salt stress responsive genes and transcription factors in developing salt tolerant transgenics crops can also provide significant benefits, and potentially boost the agricultural industry for sustainable growth and production.

Homeostasis of inorganic phosphate (P_i) in the chloroplasts is essential for healthy CO₂ assimilation. When P_i in chloroplasts is insufficient, the increase in the CO₂ assimilation rate (A) with an increase in CO₂ level is restricted, whereas A per unit total protein level moderately decreases under low-to-normal CO₂ levels. Some phosphate transporters (PHT) are localized in the chloroplast envelope; however, their contribution to the maintenance of P_i homeostasis for CO₂ assimilation has rarely been reported. In this study, we generated transgenic rice plants with RNAi-suppressed PHT4;4, one of the two genes of chloroplast envelope-localized PHT, and examined the changes in the characteristics of CO₂ assimilation. In three transgenic lines, the mRNA levels of PHT4;4 decreased by approximately 80% without a notable decrease in total leaf-P levels or total leaf-N levels, which is thought to approximately correspond to total protein levels. A in the transgenic plants tended to be slightly lower than that in the wild-type plants, irrespective of the CO₂ level, and typically increased to saturation with increasing CO₂ levels. A per unit total leaf-N level in transgenic plants tended to be slightly lower than that in wild-type plants. These results indicate that substantial PHT4;4 suppression caused slight symptoms of P_i-limited CO₂ assimilation. Therefore, PHT4;4 is suggested to be involved in the maintenance of chloroplast P_i homeostasis for healthy CO₂ assimilation, although its contribution is minor.

Diversity of endemic species may result from two evolutionary processes: in-situ diversification (radiation) or phylogenetically independent divergences (non-radiation). To explore the evolutionary history of endemic-rich alpine flora in the Japanese Archipelago, we investigated the phylogenetic relationships of four endemic taxa of Draba (Brassicaceae) from the high mountains of central Honshu: D. kitadakensis, D. sachalinensis var. shinanomontana, D. sakuraii var. nipponica, and D. shiroumana. Using molecular phylogenetic analyses on plastid trnL-F and nuclear ITS sequence of 157 taxa, we found that the four taxa endemic to central Honshu did not form a monophyletic group and diverged from at least two evolutionary independent lineages. Moreover, ancestral area reconstruction further revealed that some of their ancestral species may have originated from different geographical regions. These findings indicate that the endemic Draba in central Honshu diverged through non-radiative evolutionary origin. Our study suggests that the richness of endemic species in the alpine zone of the Japanese Archipelago is associated with multiple sources with high species diversity located in nearby geographical regions.

Pollen is required for fertilization and the associated production of seeds and fruits, which are important for human nutrition. Research on the tricellular pollen of Arabidopsis thaliana revealed that chromatin is highly condensed and transcriptional activity is suppressed in sperm cells. However, comprehensive structural investigations involving generative cells of bicellular pollen have not been conducted. In this study, we provide relevant insights into other angiosperms that produce bicellular pollen. Lilium longiflorum, which has large and easily observable nuclei, was used for a detailed analysis of the chromatin structure and transcriptionally active regions in pollen and pollen tubes. Chromatin was condensed, resulting in a ribbon-like structure that was clearly visible in mature generative cell nuclei. Additionally, transcriptionally active regions were restricted to the intersections of chromatin as pollen desiccated. Although de novo transcription was revealed to be unnecessary for pollen tube growth, transcriptional activity temporarily resumed before generative cell division during pollen tube growth. Moreover, the inhibition of de novo transcription influenced changes in nuclear morphology. In this study, the distinctive chromatin structures and transcriptional activity states in generative cell nuclei of bicellular pollen were elucidated, with the generated data contributing to a deeper understanding of transcription and other regulatory mechanisms involved in pollen maturation and pollen tube growth.