Background: Phoebe zhennan and Phoebe chekiangensis are valuable evergreen trees recognized for their unique aromas and ecological significance, yet the organ-related distribution and functional implications of aroma-active volatiles remain insufficiently characterized. Methods: In this study, we applied an integrated GC-MS-based volatile metabolomics approach combined with a relative odor activity value (rOAV) analysis to comprehensively profile and compare the volatile metabolite landscape in the seeds and leaves of both species. Results: In total, 1666 volatile compounds were putatively identified, of which 540 were inferred as key aroma-active contributors based on the rOAV analysis. A multivariate statistical analysis revealed clear tissue-related separation: the seeds were enriched in sweet, floral, and fruity volatiles, whereas the leaves contained higher levels of green leaf volatiles and terpenoids associated with ecological defense. KEGG pathway enrichment indicated that terpenoid backbone and phenylpropanoid biosynthesis pathways played major roles in shaping these divergent profiles. A Venn diagram analysis further uncovered core and unique volatiles underlying species and tissue specificity. Conclusions: These insights provide an integrated reference for understanding tissue-divergent volatile profiles in Phoebe species and offer a basis for fragrance-oriented selection, ecological trait evaluation, and the sustainable utilization of organ-related metabolic characteristics in breeding and conservation programs.

Drought severely affects the growth and production of pecan (Carya illinoinensis), while genes conferred drought adaptation are yet to be fully elucidated. Here, an in-depth exploration of the two different RNA-seq projects regarding drought stress (designated as P1 and P2) was performed via weighted gene co-expression network analysis. For the two projects, there existed one pair of modules (P1 turquoise module and P2 blue module) that was probably associated with drought resistance, as the paired modules both exhibited an increased expression profile with increasing water shortage stress and were annotated to be involved in oxidative stress response and the signaling pathways of abscisic acid and jasmonic acid. There were 441 and 1258 hub genes in the P1 turquoise module and P2 blue module, respectively, among which, 140 were overlapped and thus were recognized as core drought responsive genes. An additional drought stress experiment was conducted for RT-qPCR validation, and the results showed that the 20 core genes selected for detection were highly responsive to water deficit. Together, our results will be helpful for understanding the molecular mechanism of drought response and improving drought resistance in pecan.

Response regulator (RR) is the core component of cytokinin (CK) signaling, and it regulates the expression of numerous downstream CK-responsive genes. However, the knowledge regarding the pecan RR (CiRR) gene family is still limited. In this study, we first monitored trans-zeatin riboside (tZR) content in the graft union 0, 7, 14, and 32 days after grafting and then conducted genome-wide analysis and expression profiling of the CiRR gene family using an available genome sequence and RNA-seq dataset, aiming to better understand the roles of CK during pecan grafting. The dynamic contents of tZR showed an increased trend during the specific period for both the scion and rootstock. There were 20 CiRRs in the pecan genome, including 12 type A CiRRs, 5 type B members, and 3 type C genes. All members contained a receiver domain and type B CiRRs possessed an additional Myb-like DNA-binding domain. Promoter analysis showed that the CiRR gene family contained cis-elements associated with growth and development, hormones, and stress. A total of 10 genes, including CiRR18/9/4a/14a/12c/5/12b/14b/2b/2a, were abundantly expressed in the samples of different tissues, drought stress, and kernel development. There were 12 genes (CiRR5/18/4a/12b/2b/12c/14b/2a/14a/4b/9/11a) showing active expressions during grafting, and weighted gene co-expression network analysis (WGCNA) grouped them into six modules. Among them, CiRR14a and CiRR12b were the hub genes for the turquoise and brown modules, respectively. Functional annotation indicated that the turquoise module was associated with gene transcription and translation, while the brown module was related to cell proliferation. Our results suggest that the CiRR gene family central to CK signaling is probably involved in callus formation during pecan grafting.

Salt stress severely limits the growth and ornamental value of pecan (Carya illinoinensis) in salinized regions, yet the transcriptional mechanisms underlying its stress adaptation remain unclear. In this study, a comprehensive genomic analysis of the GRAS transcription factor family identified 58 CiGRAS genes in pecan. These genes were classified into 11 subfamilies and showed conserved motifs and gene structures, with variation in promoter cis-elements suggesting diverse regulatory functions. Chromosomal distribution and duplication analysis indicated that whole-genome and dispersed duplication events were the main drivers of CiGRAS expansion. Transcriptome data revealed tissue-specific expression and strong responsiveness to salt and other stresses. Under 0.6% NaCl treatment, several CiGRAS genes were significantly upregulated, especially at 48 h. Gene co-expression analysis further highlighted GRAS-enriched modules associated with redox regulation and stress signaling. qRT-PCR validation confirmed time-specific induction of seven CiGRAS genes under salt stress. These findings provide insights into the evolutionary dynamics and stress-related roles of CiGRAS genes and offer candidate regulators for improving pecan salt tolerance in ecological greening and landscape applications.