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Plantago is a major genus belonging to the Plantaginaceae family and is used in herbal medicine, functional food, and pastures. Several Plantago species are also characterized by their global distribution, but the mechanism underpinning this is not known. Here, we present a high-quality, chromosome-level genome assembly of Plantago major L., a species of Plantago, by incorporating Oxford Nanopore sequencing and Hi-C technologies. The genome assembly size was approximately 671.27 Mb with a contig N50 length of 31.30 Mb. 31,654 protein-coding genes were identified from the genome. Evolutionary analysis showed that P. major diverged from other Lamiales species at ~62.18 Mya and experienced two rounds of WGD events. Notably, many gene families related to plant acclimation and adaptation expanded. We also found that many polyphenol biosynthesis genes showed high expression patterns in roots. Some amino acid biosynthesis genes, such as those involved in histidine synthesis, were highly induced under metal (Ni) stress which led to the accumulation of corresponding metabolites. These results suggest persuasive arguments for the global distribution of P. major through multiscale analysis. Decoding the P. major genome provides a valuable genomic resource for research on dissecting biological function, molecular evolution, taxonomy, and breeding

Vertical stratification in trees may respond to selective pressures to enhance light interception and utilization; therefore, the vertical functional variation in leaf traits may indicate niche partitioning within forests. In this study, vertical variations in leaf and crown structure traits of seven common tree species were analysed with respect to differences between species in different height groups, within the same height range, in the same species across tree height, and different parts of the individual tree crown to reveal coexistence mechanisms in subtropical forest tree species. There were multiple levels of trait variation in the vertical dimension, validating the existence of vertical niche differentiation in subtropical forest species. The functional trait differences arose among different height groups, among species co-occurring within the same height range, in the same species across tree height, and among different parts of the individual tree crown. Variation in comparative advantages, which was characterised by those traits between species across different height ranges, was also one of the manifestations of niche differentiation in the vertical dimension. Moreover, contrasting results between lower height ranges and higher ranges in the relationship between species’ differences in functional traits and species’ difference of abundance were found, further confirming that there was obvious vertical niche separation in the community. This study emphasised the importance of vertical variation in species’ performances in elucidating the mechanisms of tree species coexistence in subtropical forests.

Plant metal tolerance proteins (MTPs) play key roles in heavy metal absorption and homeostasis in plants. By using genome-wide and phylogenetic approaches, the origin and diversification of MTPs from Canavalia rosea (Sw.) DC. was explored. Canavalia rosea (bay bean) is an extremophile halophyte with strong adaptability to seawater and drought and thereby shows specific metal tolerance with a potential phytoremediation ability. However, MTP genes in leguminous plants remain poorly understood. In our study, a total of 12 MTP genes were identified in C. rosea. Multiple sequence alignments showed that all CrMTP proteins possessed the conserved transmembrane domains (TM1 to TM6) and could be classified into three subfamilies: Zn-CDFs (five members), Fe/Zn-CDFs (five members), and Mn-CDFs (two members). Promoter cis-acting element analyses revealed that a distinct number and composition of heavy metal regulated elements and other stress-responsive elements existed in different promoter regions of CrMTPs. Analysis of transcriptome data revealed organ-specific expression of CrMTP genes and the involvement of this family in heavy metal stress responses and adaptation of C. rosea to extreme coral reef environments. Furthermore, the metal-specific activity of several functionally unknown CrMTPs was investigated in yeast. These results will contribute to uncovering the potential functions and molecular mechanisms of heavy metal absorption, translocation, and accumulation in C. rosea plants.

Canavalia rosea (bay bean), distributing in coastal areas or islands in tropical and subtropical regions, is an extremophile halophyte with good adaptability to seawater and drought. Late embryogenesis abundant (LEA) proteins typically accumulate in response to various abiotic stresses, including dehydration, salinity, high temperature, and cold, or during the late stage of seed development. Abscisic acid-, stress-, and ripening-induced (ASR) genes are stress and developmentally regulated plant-specific genes. In this study, we reported the first comprehensive survey of the LEA and ASR gene superfamily in C. rosea. A total of 84 CrLEAs and three CrASRs were identified in C. rosea and classified into nine groups. All CrLEAs and CrASRs harbored the conserved motif for their family proteins. Our results revealed that the CrLEA genes were widely distributed in different chromosomes, and all of the CrLEA/CrASR genes showed wide expression features in different tissues in C. rosea plants. Additionally, we introduced 10 genes from different groups into yeast to assess the functions of the CrLEAs/CrASRs. These results contribute to our understanding of LEA/ASR genes from halophytes and provide robust candidate genes for functional investigations in plant species adapted to extreme environments.

Canavalia rosea (bay bean), distributing in coastal areas or islands in tropical and subtropical regions, is an extremophile halophyte with good adaptability to seawater and drought. Late embryogenesis abundant (LEA) proteins typically accumulate in response to various abiotic stresses, including dehydration, salinity, high temperature, and cold, or during the late stage of seed development. Abscisic acid-, stress-, and ripening-induced (ASR) genes are stress and developmentally regulated plant-specific genes. In this study, we reported the first comprehensive survey of the LEA and ASR gene superfamily in C. rosea. A total of 84 CrLEAs and three CrASRs were identified in C. rosea and classified into nine groups. All CrLEAs and CrASRs harbored the conserved motif for their family proteins. Our results revealed that the CrLEA genes were widely distributed in different chromosomes, and all of the CrLEA/CrASR genes showed wide expression features in different tissues in C. rosea plants. Additionally, we introduced 10 genes from different groups into yeast to assess the functions of the CrLEAs/CrASRs. These results contribute to our understanding of LEA/ASR genes from halophytes and provide robust candidate genes for functional investigations in plant species adapted to extreme environments.

Background: Canavalia rosea (Sw.) DC. (bay bean) is an extremophile halophyte that is widely distributed in coastal areas of the tropics and subtropics. Seawater and drought tolerance in this species may be facilitated by aquaporins (AQPs), channel proteins that transport water and small molecules across cell membranes and thereby maintain cellular water homeostasis in the face of abiotic stress. In C. rosea, AQP diversity, protein features, and their biological functions are still largely unknown.Results: We describe the action of AQPs in C. rosea using evolutionary analyses coupled with promoter and expression analyses. A total of 37 AQPs were identified in the C. rosea genome and classified into five subgroups: 11 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, 11 Nod26-like intrinsic proteins, 4 small and basic intrinsic proteins, and 1 X-intrinsic protein. Analysis of RNA-Seq data and targeted qPCR revealed organ-specific expression of aquaporin genes and the involvement of some AQP members in adaptation of C. rosea to extreme coral reef environments. We also analyzed C. rosea sequences for phylogeny reconstruction, protein modeling, cellular localizations, and promoter analysis. Furthermore, one of PIP1 gene, CrPIP1;5, was identified as functional using a yeast expression system and transgenic overexpression in Arabidopsis.Conclusions: Our results indicate that AQPs play an important role in C. rosea responses to saline-alkaline soils and drought stress. These findings not only increase our understanding of the role AQPs play in mediating C. rosea adaptation to extreme environments, but also improve our knowledge of plant aquaporin evolution more generally.

Aquaporins are channel proteins that facilitate the transmembrane transport of water and other small neutral molecules, thereby playing vital roles in maintaining water and nutrition homeostasis in the life activities of all organisms. Canavalia rosea, a seashore and mangrove-accompanied halophyte with strong adaptability to adversity in tropical and subtropical regions, is a good model for studying the molecular mechanisms underlying extreme saline-alkaline and drought stress tolerance in leguminous plants. In this study, a PIP2 gene (CrPIP2;3) was cloned from C. rosea, and its expression patterns and physiological roles in yeast and Arabidopsis thaliana heterologous expression systems under high salt-alkali and high osmotic stress conditions were examined. The expression of CrPIP2;3 at the transcriptional level in C. rosea was affected by high salinity and alkali, high osmotic stress, and abscisic acid treatment. In yeast, the expression of CrPIP2;3 enhanced salt/osmotic and oxidative sensitivity under high salt/osmotic and H2O2 stress. The overexpression of CrPIP2;3 in A. thaliana could enhance the survival and recovery of transgenic plants under drought stress, and the seed germination and seedling growth of the CrPIP2;3 OX (over-expression) lines showed slightly stronger tolerance to high salt/alkali than the wild-type. The transgenic plants also showed a higher response level to high-salinity and dehydration than the wild-type, mostly based on the up-regulated expression of salt/dehydration marker genes in A. thaliana plants. The reactive oxygen species (ROS) staining results indicated that the transgenic lines did not possess stronger ROS scavenging ability and stress tolerance than the wild-type under multiple stresses. The results confirmed that CrPIP2;3 is involved in the response of C. rosea to salt and drought, and primarily acts by mediating water homeostasis rather than by acting as an ROS transporter, thereby influencing physiological processes under various abiotic stresses in plants.

The sequestration of soil organic carbon (SOC) in terrestrial ecosystems is determined by the balance between plant- and microbial-derived carbon inputs and losses through soil respiration. However, a consensus on the elevational patterns of soil microbial necromass and its contribution to SOC is rare, and the information on how climatic and edaphic factors affect the accumulation of microbial necromass remains limited. In this study, soil samples were collected with a 50-m interval along an elevational gradient (200–950 m above sea level) to investigate the effects of climatic and edaphic variability associated with elevation and season on microbial necromass in subtropical forests. The concentration of soil amino sugar was measured by high-performance liquid chromatography (HPLC) to characterize soil microbial necromass. Partial least squares path modeling (PLS-PM) was used for testing climatic and edaphic controls over the elevational pattern of microbial necromass. The concentration of soil microbial necromass and its contribution to SOC were affected by elevation and season, with lower concentration and contribution in the wet season than in the dry season. Soil microbial necromass linearly increased or followed a quadratic pattern with elevation, and accounted for 18.9% of SOC on average with a greater contribution from fungal necromass (13.2%) than from bacterial necromass (5.7%). Soil temperature, soil nitrogen and moisture content directly influenced the accumulation of soil microbial necromass with varied effects on fungal and bacterial necromass. Warmer and nutrient-impoverished environments were linked with the depletion of fungal necromass, whereas higher soil moisture and nutrient availability were positively associated with the accumulation of bacterial necromass. Our findings demonstrate that less microbial necromass, especially fungal necromass will accumulate in SOC in response to future climate warming in subtropical forests. Such information is valuable for improving our understanding of the potential impacts of future climatic change on soil carbon cycling in subtropical regions.

Aquaporins are channel proteins that facilitate the transmembrane transport of water and other small neutral molecules, thereby playing vital roles in maintaining water and nutrition homeostasis in the life activities of all organisms. Canavalia rosea, a seashore and mangrove-accompanied halophyte with strong adaptability to adversity in tropical and subtropical regions, is a good model for studying the molecular mechanisms underlying extreme saline-alkaline and drought stress tolerance in leguminous plants. In this study, a PIP2 gene (CrPIP2;3) was cloned from C. rosea, and its expression patterns and physiological roles in yeast and Arabidopsis thaliana heterologous expression systems under high salt-alkali and high osmotic stress conditions were examined. The expression of CrPIP2;3 at the transcriptional level in C. rosea was affected by high salinity and alkali, high osmotic stress, and abscisic acid treatment. In yeast, the expression of CrPIP2;3 enhanced salt/osmotic and oxidative sensitivity under high salt/osmotic and H2O2 stress. The overexpression of CrPIP2;3 in A. thaliana could enhance the survival and recovery of transgenic plants under drought stress, and the seed germination and seedling growth of the CrPIP2;3 OX (over-expression) lines showed slightly stronger tolerance to high salt/alkali than the wild-type. The transgenic plants also showed a higher response level to high-salinity and dehydration than the wild-type, mostly based on the up-regulated expression of salt/dehydration marker genes in A. thaliana plants. The reactive oxygen species (ROS) staining results indicated that the transgenic lines did not possess stronger ROS scavenging ability and stress tolerance than the wild-type under multiple stresses. The results confirmed that CrPIP2;3 is involved in the response of C. rosea to salt and drought, and primarily acts by mediating water homeostasis rather than by acting as an ROS transporter, thereby influencing physiological processes under various abiotic stresses in plants.

The PAS domains are signal modules, which are widely distributed in proteins across all kingdoms of life. They are common in photoreceptors and transcriptional regulators of eukaryotic circadian clocks q(bHLH-PAS proteins and PER in animals; PHY and ZTL in plants; and WC-1, 2, and VVD in fungi) and possess mainly protein–protein interaction and light-sensing functions. We conducted several evolutionary analyses of the PAS superfamily. Although the whole superfamily evolved primarily under strong purifying selection (average ω ranges from 0.0030 to 0.1164), some lineages apparently experienced strong episodic positive selection at some periods of the evolution. Although the PAS domains from different proteins vary in sequence and length, but they maintain a fairly conserved 3D structure, which is determined by only eight residues. The WC-1 and WC- 2, bHLH-PAS, and P er genes probably originated in the Neoproterozoic Era (1000–542 Mya), plant P hy and ZTL evolved in the Paleozoic (541–252 Mya), which might be a result of adaptation to the major climate and global light regime changes having occurred in those eras.

Circadian rhythmicity is an endogenous biological cycle of about 24 h, which exists in cyanobacteria and fungi, plants and animals. Circadian rhythms improve the adaptability of organisms in both constant and changing environments. The cryptochrome (CRY) is a key element of the circadian system in various animal groups including fishes. We studied evolution of cryptochromes in the phylogenetically and ecologically diverse fish taxa. The phylogenetic tree of fish Cry features two major clades: Cry1 and Cry2. Teleosts possess extra copies of Cry1 due to the genome duplication, which resulted in 3 main paralogous subfamilies (1A, 1B and 1C). Cry1 experienced further diversification through additional duplications in some taxa. 1A of Cry1 is more conserved than the other paralogs (dN = 0.010 ± 0.003, π = 0.119 ± 0.058). The analysis of selection indicated that, while the Cry homologs in fish evolved under the different levels of selection pressure, strong purifying selection (average ω = 0.017) dominated in their evolution.