With the increasing power of DNA sequencing, the genomics-based approach is becoming a promising resolution to dissect the molecular mechanism of domestication of complex traits in trees. Genus Camellia possesses rich resources with a substantial value for producing beverage, ornaments, edible oil and more. Currently, a vast number of genetic and genomic research studies in Camellia plants have emerged and provided an unprecedented opportunity to expedite the molecular breeding program. In this paper, we summarize the recent advances of gene expression and genomic resources in Camellia species and focus on identifying genes related to key economic traits such as flower and fruit development and stress tolerances. We investigate the genetic alterations and genomic impacts under different selection programs in closely related species. We discuss future directions of integrating large-scale population and quantitative genetics and multiple omics to identify key candidates to accelerate the breeding process. We propose that future work of exploiting the genomic data can provide insights related to the targets of domestication during breeding and the evolution of natural trait adaptations in genus Camellia.

Crassulacean acid metabolism (CAM) is an important photosynthetic pathway for plant adaptation to dry environments. CAM plants feature a coordinated interaction between mesophyll and epidermis functions that involves refined regulations of gene expression. Plant microRNAs (miRNAs) are crucial post-transcription regulators of gene expression, however, their roles underlying the CAM pathway remain poorly investigated. Here, we present a study characterizing the expression of miRNAs in an obligate CAM species Kalanchoë marnieriana. Through sequencing of transcriptome and degradome in mesophyll and epidermal tissues under the drought treatments, we identified differentially expressed miRNAs that were potentially involved in the regulation of CAM. In total, we obtained 84 miRNA genes, and eight of them were determined to be Kalanchoë-specific miRNAs. It is widely accepted that CAM pathway is regulated by circadian clock. We showed that miR530 was substantially downregulated in epidermal peels under drought conditions; miR530 targeted two tandem zinc knuckle/PLU3 domain encoding genes (TZPs) that were potentially involved in light signaling and circadian clock pathways. Our work suggests that the miR530-TZPs module might play a role of regulating CAM-related gene expression in Kalanchoë.

Camellia oleifera, a woody oilseed species endemic to China, often experiences growth constraints due to seasonal drought. This study investigates the coordinated regulation of photosynthetic traits, stomatal behavior, and hormone responses during drought–rehydration cycles in two cultivars with contrasting drought resistance: ‘CL53’ (tolerant) and ‘CL40’ (sensitive). Photosynthetic inhibition resulted from both stomatal and non-stomatal limitations, with cultivar-specific differences. After 28 days of drought, the net photosynthetic rate (Pn) declined by 26.6% in CL53 and 32.6% in CL40. A stable intercellular CO2 concentration (Ci) in CL53 indicated superior mesophyll integrity and antioxidant capacity. CL53 showed rapid Pn recovery and photosynthetic compensation post-rehydration, in contrast to CL40. Drought triggered extensive stomatal closure; >98% reopened upon rehydration, though the total stomatal pore area remained reduced. Abscisic acid (ABA) accumulation was greater in CL40, contributing to stomatal closure and Pn suppression. CL53 exhibited faster ABA degradation and gibberellin (GA3) recovery, promoting photosynthetic restoration. ABA negatively correlated with Pn, transpiration rate (Tr), stomatal conductance (Gs), and Ci, but positively with stomatal limitation (Ls). Water use efficiency (WUE) displayed a parabolic response to ABA, differing by cultivar. This integrative analysis highlights a coordinated photosynthesis–stomata–hormone network underlying drought adaptation and informs selection strategies for drought-resilient cultivars and precision irrigation.

Flowering is a key agronomic trait that directly influences the yield of the tea-oil tree (Camellia oleifera). Floral initiation, which precedes flower bud differentiation, represents a critical developmental stage affecting the flowering outcomes. However, the molecular mechanisms underlying floral initiation in C. oleifera remain poorly understood. In this study, buds from five key developmental stages of a 12-year-old C. oleifera cultivar ‘changlin53’ were collected as experimental samples. Scanning electron microscopy was employed to identify the stage of floral initiation. UPLC-MS/MS was used to analyze endogenous gibberellin (GA) concentrations, while transcriptomic analysis was performed to reveal the underlying transcriptional regulatory network. Six GA types were detected during floral initiation and petal development. GA₄ was exclusively detected at the sprouting stage (BII), while GA₃ was present in all samples but was significantly lower in BII and the flower bud primordium formation stage (BIII) than in the other samples. A total of 64 differentially expressed genes were concurrently enriched in flower development, reproductive shoot system development, and shoot system development. Weighted gene co-expression network analysis (WGCNA) identified eight specific modules significantly associated with different developmental stages. The magenta module, containing Unigene0084708 (CoFT) and Unigene0037067 (CoLEAFY), emerged as a key regulatory module driving floral initiation. Additionally, GA20OX1 and GA2OX8 were identified as candidate genes involved in GA-mediated regulation of floral initiation. Based on morphological and transcriptomic analyses, we conclude that floral initiation of C. oleifera is a continuous regulatory process governed by multiple genes, with the FT-LFY module playing a central role in the transition from apical meristem to floral meristem.

Camellia oleifera is an important woody oil plant in southern China, and developing its industry can enhance forest resource uses and increase edible oil supply. This study investigated the floral characteristics of different C. oleifera varieties, analysed the species and diversity of flower-visiting insects in different habitats, identified the main pollinators and their flower-visiting behaviours, and explored the relationship between pollinating insects and their floral characteristics. The floral lifespan of individual C. oleifera flowers was 5–8 d across cultivars, which is essentially the same. However, floral traits and nectar sugar composition exhibited distinct differences. There were 22 species of insect pollinators from 14 genera and 8 families, including Hymenoptera and Diptera, in 3 habitats. High-potential pollinators varied by habitat, with Apis cerana and Phytomia zonata being the most frequent. A comparison showed that A. cerana was the best pollinator, whereas P. zonata had a larger population, was not affected by oil tea nectar poisoning, and could still pollinate. Therefore, the contribution of P. zonata cannot be overlooked. Redundancy analysis revealed the response relationship between the floral traits of C. oleifera and three insect population characteristics. Stamen length was the main floral trait affecting insect populations.

Kadsura coccinea (Lem.) A. C. Smith is a significant tree species of non-timber forest. However, the low germination percentage and lengthy germination time of its seeds pose obstacles to industry development. Aiming at the problem of seed dormancy, this study first determined the seed dormancy period through seed germination test, and then comprehensively evaluated the dormancy characteristics by observing the seed coat structure, measuring endogenous inhibitors, and in vitro embryo culture. The results indicated the dormancy of K. coccinea seeds, and that the germination period was up to 80 days. Its seed coat is composed of exotesta and endotesta. The dense seed coat structure causes water absorption and air permeability obstacles to the seeds and causes mechanical restraint to the development of the embryo. Meanwhile, its seeds have substances that inhibit seed germination, and there are germination inhibitors in distilled water, methanol, petroleum ether, and ethyl acetate extracts of kernels and seed coats. The inhibitory activity of kernel petroleum ether extract was the highest, and the inhibitory activity of seed coat methanol extract was the highest. In addition, the embryo of K. coccinea developed completely and could germinate normally under in vitro conditions. This study has basically proved that the dormancy of K. coccinea seeds is caused by the seed coat (physical dormancy) and endogenous inhibitors (physiological dormancy), which provides a scientific theoretical basis to further explore the method of seed dormancy release of K. coccinea.