Search Results (43)

The Sugars Will Eventually be Exported Transporters (SWEET) family plays a crucial role in the carbohydrate distribution, phloem loading, and stress response of plants, yet the evolutionary characteristics and functional diversification of SWEET genes in the endangered timber species Phoebe bournei (Hemsl.) Yen C. Yang remain largely unexplored. In this study, 21 PbSWEET genes were identified and classified into four subfamilies (A-D). Subfamily A exhibited a unique lineage expansion, mainly driven by tandem and segmental duplications. The nonsynonymous-to-synonymous substitution ratio (Ka/Ks) values of all duplicate gene pairs were all less than 1, indicating a strong selective suppression effect; consistent with this evolutionary constraint, the majority of PbSWEET proteins harbor the conserved Medicago truncatula Nodulin 3/saliva (MtN3_slv) domain, with only a few exceptions lacking a complete version. Promoter and hormone response analyses revealed that under abscisic acid (ABA) stress, PbSWEET4 exhibited an immediate burst, whereas PbSWEET10 showed a delayed burst. Physiological data indicated that soluble sugars may be more dominant osmolytes than proline (Pro), a pattern that points to a potential carbon-centric regulatory strategy. PbSWEET4 showed an early burst before sugar/oxidative peaks, suggesting a possible non-canonical signaling role, whereas PbSWEET10 exhibited a late increase coinciding with sugar/malondialdehyde (MDA) peaks, suggesting potential involvement in sugar redistribution. Under methyl jasmonate (MeJA) treatment, PbSWEET10 was rapidly induced, yet sugar accumulation occurred only at 24 h, a temporal decoupling that suggests a possible transcription–metabolism decoupling. Collectively, these correlative patterns point to a possible dual-wave transcriptional mechanism and nominate PbSWEET10 as a candidate for stress response, though these inferences require functional validation. Full article

Cold sensitivity restricts the natural distribution of subtropical evergreen trees. In a representative species such as Phoebe bournei, evaluating physiological divergence among provenances is therefore essential for identifying cold-hardy germplasm and understanding adaptive evolution. This study investigated the photosynthetic capacity, redox homeostasis, and carbon metabolism of saplings from three provenances (WY, AF, and SC) under chilling stress and subsequent recovery. The results showed that low temperature significantly inhibited the net photosynthetic rate and photochemical efficiency in all saplings through predominant non-stomatal limitations. The northern provenance WY prioritized structural integrity and redox homeostasis by enhancing cyclic electron flow and timely antioxidant activation. The mid-latitude provenance AF demonstrated higher physiological plasticity and achieved more rapid recovery of photosynthetic activity upon rewarming. In contrast, the southern provenance SC was highly sensitive to chilling stress, exhibiting disrupted energy dissipation, severe lipid peroxidation, and impaired coordination of carbon metabolism and hormonal regulation. Overall, the pronounced divergence in adaptive strategies among provenances is evident. These findings provide a physiological basis for understanding intraspecific variation in P. bournei and offer guidance for germplasm selection under climate change. Full article

Phoebe bournei is a precious timber species unique to China, possessing significant ornamental, ecological, and medicinal values. The polyembryonic phenomenon is widely observed in its seeds, but the underlying mechanisms driving its formation remain unclear. In this study, an integrated analysis was conducted for polyembryony formation in P. bournei seeds, including biochemical indicators, environmental factors, and transcriptional levels. Firstly, morphological observation of seeds from 13 plus trees showed no significant correlation between polyembryony rate and external environment or seed morphology. Subsequently, comparative transcriptomic analysis between monoembryonic and polyembryonic seeds identified 1957 differentially expressed genes (DEGs), which were significantly enriched in biological processes and pathways including photosystem II, tetrapyrrole binding, heme binding, and phenylpropanoid biosynthesis, indicating the probable effect of gene regulation in polyembryony formation. Furthermore, eight RWP transcription factors were identified, potentially involved in polyembryony. qRT-PCR analysis revealed that the expression levels of PbRWP2 and PbRWP5 were significantly upregulated in polyembryonic seeds, indicating they may be key regulatory genes during polyembryony formation in P. bournei seeds. This study preliminarily explored the transcriptomic characterization and potential molecular regulatory basis of polyembryony formation in P. bournei, laying a critical foundation for further deciphering the intricate mechanisms governing its polyembryonic development. Full article

Water availability and light conditions are among the most important environmental factors affecting tree growth and development. The FAR1/FHY3 (FRS) gene family consists of transposase-derived transcription factors that are widely involved in light signaling and responses to environmental stresses. Although FRS genes have been characterized in several plant species, a comprehensive analysis in P. bournei is still lacking. In this study, we performed the first comprehensive genome-wide analysis of the FRS gene family in P. bournei, including physicochemical characterization, chromosomal localization, phylogenetic analysis, gene structure and conserved motif analysis, protein structure prediction, promoter cis-element analysis, organ/tissue expression profiling, and RT-qPCR analysis under PEG-induced osmotic stress, full-light, and shade treatments. A total of 21 PbFRS genes were identified and found to be unevenly distributed across 11 chromosomes. Phylogenetic analysis, together with Arabidopsis thaliana and Zea mays FRS proteins, clustered the family members into five clades, including one P. bournei-specific clade, suggesting lineage-specific expansion and possible functional diversification. Structural analyses revealed both conserved and divergent features among PbFRS members. Promoter analysis identified diverse cis-acting elements related to light, temperature, hormones, and stress responses, suggesting that PbFRS genes may have diverse regulatory potentials in response to environmental signals. Organ/tissue expression profiling further revealed clear differences in expression patterns among family members. In addition, RT-qPCR analysis showed that several genes, including PbFRS9, PbFRS10, PbFRS12, PbFRS13, PbFRS16, and PbFRS18, exhibited transcriptional responses to PEG-induced osmotic stress, full-light, and shade treatments. These results indicate that these genes may serve as candidates for future functional studies, although their direct roles in stress tolerance require further validation. Overall, these results provide the first systematic overview of the PbFRS gene family and identify transcriptionally responsive candidate genes for future functional studies in P. bournei. Full article

Phoebe bournei is a rare and economically valuable tree species native to China that plays an important ecological role. In this study, we conducted a genome-wide identification of the SQUAMOSA promoter-binding protein (SBP) transcription factor family in Phoebe bournei and characterized 19 PbSBP genes distributed across 10 chromosomes. Phylogenetic analysis grouped these genes into five distinct subfamilies, each of which showed homology to SBP genes in Arabidopsis thaliana and Oryza sativa, indicating strong evolutionary conservation within the family. All identified PbSBP proteins contain the conserved SBP domain, and some members also harbor additional motifs such as the ANK domain, which may mediate protein–protein interactions. Tissue-specific expression profiling revealed that several PbSBP genes are predominantly expressed in root bark and leaves, suggesting their potential roles in defense responses and developmental regulation. Moreover, qPCR validation showed that PbSBP2, PbSBP9, and PbSBP16 were significantly upregulated under PEG-induced drought stress, implying their involvement in abiotic stress responses. This study provides a foundational understanding of the SBP gene family in P. bournei and highlights candidate genes for future genetic improvement and breeding for stress resistance. Full article

Phosphorus deficiency restricts the productivity of plantation forests in southern China. Low-molecular-weight organic acids (LMWOAs) can promote insoluble P activation and improve P availability in red soils. However, few studies have investigated organic acids (OAs) released during litter decomposition under field conditions. A one-year litterbag decomposition experiment with monthly sampling was conducted using four common plantation tree species in subtropical China, namely, Phoebe bournei, Michelia macclurei, Schima superba, and Cunninghamia lanceolata, to determine changes in LMWOA composition, content, and release characteristics during decomposition. Seventeen LMWOAs were detected during litter decomposition, and OA types differed among tree species. The total amount of litter-derived OAs varied among species, following the order S. superba > P. bournei > C. lanceolata > M. macclurei, with the amount in S. superba being 1.15 times that in M. macclurei. The release characteristics of OAs differed significantly. C. lanceolata, S. superba, and M. macclurei exhibited a net release pattern, whereas P. bournei exhibited a release–enrichment–release pattern. S. superba and M. macclurei litter released significantly more OAs than C. lanceolata. Overall, this study provides field-based evidence for interspecific differences in litter-derived OAs dynamics and offers a basis for tree species selection in mixed plantations with potential implications for nutrient return and phosphorus cycling. Full article

Native tree species play a crucial role in addressing the challenge of seasonal drought in South China. In this study, one-year-old seedlings of eight native tree species in Guangdong Province were subjected to continuous simulated drought stress and rewatering. In order to identify key drought-resistant traits and best performing tree species, physiological and biochemical responses were assessed through 21 indicators. The results showed the following: (1) All species exhibited responses to drought stress prior to the fourth day, as evidenced by reductions in morphological indicators (crown breadth and ground diameter) and photosynthetic parameters (chlorophyll content, transpiration rate, net photosynthetic rate and stomatal conductance), along with increases in osmotic substances (soluble protein and proline) and antioxidant-related indicators malondialdehyde, peroxidase and superoxide dismutase). (2) The crown breadth, leaf relative water content, chlorophyll content, and ascorbate peroxidase activity were significantly decreased under drought stress. And these indicators were not recovered to pre-stress levels following rewatering. (3) Mantel tests revealed that growth morphological characteristics, particularly plant height, were significantly and positively correlated with most osmotic substances indicators (p < 0.001). Specifically, plant height showed the strongest coupling with these traits, with Mantel’s r ranging from 0.44 to 0.89. In addition, the leaf relative water content, net photosynthetic rate, superoxide dismutase, and malondialdehyde were regarded as the key drought-resistant traits, providing insights into future research on plant improvement, stress-resilience breeding and even drought resistance mechanisms. (4) The eight tree species are ranked from most to least drought-resistant as follows: Zenia insignis, Michelia macclurei, Phoebe zhennan, Phoebe bournei, Erythrophleum fordii, Dalbergia odorifera, Cinnamomum burmanni and Michelia chapensis. This study provides a scientific basis for selecting tree species for afforestation in seasonally arid regions. Full article

Endophytic fungi enhance plant growth and stress resilience, yet their molecular roles in the roots of the endangered tree Phoebe bournei remain unclear. A comparative RNA-seq analysis was performed on root transcriptomes from wild, endophyte-colonized adult trees (OT) and axenically grown seedlings (ST). Unmapped reads were analyzed against the NCBI nucleotide (NT) database using BLASTN (v2.17.0), revealing Rhizophagus irregularis as the predominant endophytic fungus. Differential expression analysis identified 5891 DEGs, which were significantly enriched in pathways related to plant–pathogen interactions, phenylpropanoid biosynthesis, plant hormone signal transduction, and MAPK signaling. Key upregulated genes included PbMPK3, PbCML42, PbCML41.2, and PbGSTU28, suggesting enhanced ROS scavenging, calcium signaling, and defense activation. RT-qPCR validation confirmed the transcriptomic trends for selected genes. Our findings reveal that root endophytic fungi modulate a coordinated network involving immune priming, phytohormone regulation, and redox homeostasis, thereby supporting root development and enhancing resistance to biotic and abiotic stresses in P. bournei. This study provides foundational molecular insights into beneficial plant–endophyte interactions and identifies candidate genes that are valuable for the conservation and breeding of this threatened species. Full article

Phoebe bournei is an important economic tree species in China, its large-scale propagation is limited by the difficulty of adventitious root (AR) formation in cuttings. In this study, morphological, physiological, and transcriptomic analyses were conducted to investigate the process of AR formation in P. bournei. The results showed that ARs mainly originated from callus tissue. During AR formation, soluble sugar and soluble protein contents changed significantly. Malondialdehyde (MDA) and oxygen free radicals (OFRs) peaked at first sampling stage (PB0), while the activities of polyphenol oxidase (PPO) and indoleacetic acid oxidase (IAAO) exhibited similar patterns. Lignin content increased during callus induction stage, whereas phenolic content continuously declined throughout rooting. Endogenous hormone levels also changed markedly, and Orthogonal partial least squares discriminant analysis (OPLS-DA) analysis indicated that indole-3-acetic acid (IAA) and abscisic acid (ABA) played dominant roles in this process. KEGG enrichment analysis revealed significant enrichment of the phenylpropanoid biosynthesis pathway in all three comparison groups. A total of 48 differentially expressed genes (DEGs) were enriched in plant hormone signal transduction pathways, with 22 and 14 genes associated with IAA and ABA signaling, respectively. Weighted gene co-expression network analysis (WGCNA) further identified two hub modules related to IAA and ABA contents, including eight hub genes such as D6PKL1 and ISTL1. Correlation analysis revealed that the hub genes D6PKL1 and HSP were significantly positively correlated with IAA4 in the IAA signaling pathway. Overall, this study provides new insights into the mechanisms underlying AR formation in P. bournei cuttings and offers a theoretical basis for optimizing its clonal propagation system. Full article

Trees in the genus Phoebe of the Lauraceae family are commonly known as “Nanmu” in traditional Chinese culture. As they have offered highly valued timbers for construction, furniture, and coffins since the pre-Qin Dynasty, it is crucial to identify and protect these Phoebe species. However, the accuracy of Phoebe species identification is frequently hampered due to the limitations of traditional morphological and wood anatomy methods as the marker characteristics are very similar between the species, alongside the requirement for specialized expertise. Here, we use DNA barcoding technology for the rapid and accurate identification of five endangered Phoebe species in China, including Phoebe bournei, P. chekiangensis, P. hui, P. sheareri and P. zhennan. Four highly divergent regions (petA-psbJ-psbL-psbF-psbE, Ψycf1-ndhF, rpl32-trnL^UAG and ycf1) were identified from a comparison of the 20 Phoebe plastomes downloaded from the database. Furthermore, phylogenetic analysis on 20 Phoebe species showed that rpl32-trnL^UAG + ycf1, as well as rpl32-trnL^UAG + ycf1 + Ψycf1-ndhF, effectively distinguished the fifteen Phoebe species. We further validated the usefulness of the core 2-locus barcode using wood and leaf samples from multiple sites for five target species. The study confirms the reliability of molecular diagnostics for five Phoebe species. It also establishes critical taxonomic protocols for conserving these endangered Nanmu species in southern China. Full article

The composition and structure of understory plants are crucial for forest ecosystem succession and stability. This study examined the impact of various Cunninghamia lanceolata mixed plantation patterns on understory biodiversity, aiming to provide a theoretical foundation for sustainable management. Six patterns were evaluated using sample plots at Guanshan Forest Farm in Jiangxi Province, China. Understory vegetation diversity, biomass, and soil properties—including total nitrogen, available nitrogen, total phosphorus, available phosphorus, total potassium, available potassium, soil organic matter, and pH—were quantitatively analyzed. Significant differences in diversity among the patterns were revealed. The ‘Cunninghamia lanceolata + Phoebe bournei (Hemsl.) Yen C. Yang + Schima superba Gardner & Champ’ mixed plantation exhibited the most pronounced enhancement of understory plant diversity, whereas the ‘C. lanceolata + Liquidambar formosana Hance’ pattern demonstrated the least significant effects among all treatments. Significant correlations were detected between soil nutrients and diversity indices. Mixed patterns enhance diversity through expanded ecological niches and optimized microenvironments, thereby strengthening ecological functions and management efficiency. Full article

The bZIP gene family play a crucial role in plant growth, development, and stress responses, functioning as transcription factors. While this gene family has been studied in several plant species, its roles in the endangered woody plant Phoebe bournei remain largely unclear. This study comprehensively analyzed the PbbZIP gene family in P. bournei, identifying 71 PbbZIP genes distributed across all 12 chromosomes. The amino acid count in these genes ranged from 74 to 839, with molecular weights varying from 8813.28 Da to 88,864.94 Da. Phylogenetic analysis categorized the PbbZIP genes into 12 subfamilies (A-K, S). Interspecific collinearity analysis revealed homologous PbbZIP genes between P. bournei and Arabidopsis thaliana. A promoter cis-acting element analysis indicated that PbbZIP genes contain various elements responsive to plant hormones, stress signals, and light. Additionally, expression analysis of public RNA-seq data showed that PbbZIP genes are distributed across multiple tissues, exhibiting distinct expression patterns specific to root bark, root xylem, stem bark, stem xylem, and leaves. We also performed qRT-PCR analysis on five representative PbbZIP genes (PbbZIP14, PbbZIP26, PbbZIP32, PbbZIP67, and PbbZIP69). The results demonstrated significant differences in the expression of PbbZIP genes under various abiotic stress conditions, including salt stress, heat, and drought. Notably, PbbZIP67 and PbbZIP69 exhibited robust responses under salt or heat stress conditions. This study confirmed the roles of the PbbZIP gene family in responding to various abiotic stresses, thereby providing insights into its functions in plant growth, development, and stress adaptation. The findings lay a foundation for future research on breeding and enhancing stress resistance in P. bournei. Full article

Phoebe bournei, a rare tree species native to China, holds considerable economic importance. The heat shock protein 70 (Hsp70) family is a group of molecular chaperones that is broadly distributed across living organisms and play a critical role in processes like growth, development, and stress response. While Hsp70 genes have been identified and studied in various plant species, their specific functions in the growth and development of P. bournei remain unexplored. We performed a comprehensive analysis of the Hsp70 gene family in P. bournei, identifying a total of 45 Hsp70 genes, which were classified into four groups (I–IV) through phylogenetic analysis. All Hsp70 proteins possessed conserved structural domains, including motif 7, and introns were present in 77.8% of the genes. Chromosomal localization and collinearity analyses of the Hsp70 genes revealed their evolutionary relationships and potential gene duplication events. Examination of the cis-acting elements within the Hsp70 promoter regions revealed that the predominant elements were associated with growth and development, followed by those responsive to hormones, and then elements linked to abiotic stress. Nine genes with high expression were selected for RT-qPCR analysis. Under high-temperature stress, all nine genes were differentially upregulated, and most of these genes belonged to subfamilies II and III, indicating that these two subfamilies have strong potential for heat resistance. In this study, we have elucidated the molecular characteristics and heat response properties of the Hsp70 gene family in P. bournei, revealing the mechanisms behind its heat stress response. Our work provides a reference for stress breeding in P. bournei and a theoretical basis for the exploration of heat tolerance in woody plants. Full article

Auxin response factors (ARFs) are pivotal transcription factors that regulate plant growth, development, and stress responses. Yet, the genomic characteristics and functions of ARFs in Phoebe bournei remain undefined. In this study, 25 PbARF genes were identified for the first time across the entire genome of P. bournei. Phylogenetic analysis categorized these genes into five subfamilies, with members of each subfamily displaying similar conserved motifs and gene structures. Notably, Classes III and V contained the largest number of members. Collinearity analysis suggested that segmental duplication events were the primary drivers of PbARF gene family expansion. Structural analysis revealed that all PbARF genes possess a conserved B3 binding domain and an auxin response element, while additional motifs varied among different classes. Promoter cis-acting element analysis revealed that PbARF genes are extensively involved in hormonal responses—particularly to abscisic acid and jasmonic acid and abiotic stresses—as well as abiotic stresses, including heat, drought, light, and dark. Tissue-specific expression analysis showed that PbARF25, PbARF23, PbARF19, PbARF22, and PbARF20 genes (class III), and PbARF18 and PbARF11 genes (class V) consistently exhibited high expression levels in the five tissues. In addition, five representative PbARF genes were analyzed using qRT-PCR. The results demonstrated significant differences in the expression of PbARF genes under various abiotic stress conditions (drought, salt stress, light, and dark), indicating their important roles in stress response. This study laid a foundation for elucidating the molecular evolution mechanism of ARF genes in P. bournei and for determining the candidate genes for stress-resistance breeding. Full article

GOLDEN2-LIKE (GLK) transcription factors are crucial regulators of chloroplast development and stress responses in plants. In this study, we investigated the GLK gene family in Phoebe bournei (Hemsl.) Yen C. Yang, a near-threatened species important for forestry and wood utilization in China. We identified 61 PbGLK genes which were classified into seven subfamilies. Our analyses of their phylogenetic relationships, gene structures, and chromosomal distribution revealed diverse characteristics. Expression profiling under different tissues and abiotic stresses showed that PbGLK25 and PbGLK30 were particularly responsive to drought, heat, light, and shade stresses, with significant upregulation. These findings highlight the potential role of PbGLK genes in stress adaptation and provide insights for the genetic improvement of P. bournei. Full article