GRAS genes are important transcriptional regulators in plants that govern plant growth and development through enhancing plant hormones, biosynthesis, and signaling pathways. Drought and other abiotic factors may influence the defenses and growth of Phoebe bournei, which is a superb timber source for the construction industry and building exquisite furniture. Although genome-wide identification of the GRAS gene family has been completed in many species, that of most woody plants, particularly P. bournei, has not yet begun. We performed a genome-wide investigation of 56 PbGRAS genes, which are unequally distributed across 12 chromosomes. They are divided into nine subclades. Furthermore, these 56 PbGRAS genes have a substantial number of components related to abiotic stress responses or phytohormone transmission. Analysis using qRT-PCR showed that the expression of four PbGRAS genes, namely PbGRAS7, PbGRAS10, PbGRAS14 and PbGRAS16, was differentially increased in response to drought, salt and temperature stresses, respectively. We hypothesize that they may help P. bournei to successfully resist harsh environmental disturbances. In this work, we conducted a comprehensive survey of the GRAS gene family in P. bournei plants, and the results provide an extensive and preliminary resource for further clarification of the molecular mechanisms of the GRAS gene family in P. bournei in response to abiotic stresses and forestry improvement.

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.

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.

The BRI1 EMS suppressor 1(BES1) transcription factor is a crucial regulator in the signaling pathway of Brassinosteroid (BR) and plays an important role in plant growth and response to abiotic stress. Although the identification and functional validation of BES1 genes have been extensively explored in various plant species, the understanding of their role in woody plants—particularly the endangered species Phoebe bournei (Hemsl.) Yang—remains limited. In this study, we identified nine members of the BES1 gene family in the genome of P. bournei; these nine members were unevenly distributed across four chromosomes. In our further evolutionary analysis of PbBES1, we discovered that PbBES1 can be divided into three subfamilies (Class I, Class II, and Class IV) based on the evolutionary tree constructed with Arabidopsis thaliana, Oryza sativa, and Solanum lycopersicum. Each subfamily contains 2–5 PbBES1 genes. There were nine pairs of homologous BES1 genes in the synteny analysis of PbBES1 and AtBES1. Three segmental replication events and one pair of tandem duplication events were present among the PbBES1 family members. Additionally, we conducted promoter cis-acting element analysis and discovered that PbBES1 contains binding sites for plant growth and development, cell cycle regulation, and response to abiotic stress. PbBES1.2 is highly expressed in root bark, stem bark, root xylem, and stem xylem. PbBES1.3 was expressed in five tissues. Moreover, we examined the expression profiles of five representative PbBES1 genes under heat and drought stress. These experiments preliminarily verified their responsiveness and functional roles in mediating responses to abiotic stress. This study provides important clues to elucidate the functional characteristics of the BES1 gene family, and at the same time provides new insights and valuable information for the regulation of resistance in P. bournei.

Grasses (Poaceae) are the most economically important group of plants. Reconstructing the ancestral grass genome and studying the evolutionary factors shaping major grass lineages are crucial for understanding the evolution of cereals, including rice, wheat and maize. Here, we report a chromosome-level genome assembly of Streptochaeta spicata, which represents the lineage without typical spikelets and the sister to the rest of Poaceae, and perform comparative genomic analyses across major grass lineages. We confirm the occurrence of the ρ-whole-genome duplication (ρ-WGD) in Streptochaeta, suggesting a shared allotetraploidization event for all extant grasses. Reconstruction of the ancestral grass karyotype (AGK) reveals a chromosome number of ante-ρ (x = 8) and post-ρ (x = 12), followed by chromosome number reduction by fusion events accompanying the diversification within major subfamilies. Biased subgenome fractionation and dominance are observed and inherited across Streptochaeta and major grass lineages. Comparative expression analyses of key floral genes in S. spicata indicate that the spikelet equivalent of this early-diverging lineage might represent a modified ancestral state of grass spikelet. Given its critical phylogenetic position, the Streptochaeta genome sheds light on the early karyotypic evolution of grasses, and the origin and key morphological innovation with respect to WGDs.