Camellia nitidissima is a woody plant with high ornamental value, and its golden-yellow flowers are rich in a variety of bioactive substances, especially flavonoids, that are beneficial to human health. Chalcone isomerases (CHIs) are key enzymes in the flavonoid biosynthesis pathway; however, there is a scarcity of information regarding the CHI family genes of C. nitidissima. In this study, seven CHI genes of C. nitidissima were identified and divided into three subfamilies by phylogenetic analysis. The results of multiple sequence alignment revealed that, unlike CnCHI1/5/6/7, CnCHI2/3/4 are bona fide CHIs that contain all the active site and critical catalytic residues. Analysis of the expression patterns of CnCHIs and the total flavonoid content of the flowers at different developmental stages revealed that CnCHI4 might play an essential role in the flavonoid biosynthesis pathway of C. nitidissima. CnCHI4 overexpression significantly increased flavonoid production in Nicotiana tabacum and C. nitidissima. The results of the dual-luciferase reporter assay and yeast one-hybrid system revealed that CnMYB7 was the key transcription factor that governed the transcription of CnCHI4. The study provides a comprehensive understanding of the CHI family genes of C. nitidissima and performed a preliminary analysis of their functions and regulatory mechanisms.

Both exotic and native plant invasions can have profound impacts on ecosystems. While many studies have examined the effects of exotic plant invasions on soil properties, relatively few have tested the effects of native plant invasions on soil microbial communities. Furthermore, we know little about the effects of native plant invasions on microbial communities in litter. In subtropical forests in southern China, we sampled litter at three decomposition stages and top soil in three forest sands representing three stages of the invasion (not invaded, moderately and heavily invaded) by the Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau), a native species in China. We measured chemical properties (concentrations of C, N, P, Mg, Al, K, Ca, Mn, Cu, and Zn, and concentrations of cellulose and lignin) and microbial communities in litter and/or soil. The bamboo invasion, in general, decreased the element concentrations in litter and soil and also decreased total microbial abundance and diversity. Considering bacteria and fungi separately, the bamboo invasion decreased fungal diversity in litter and soil, but had little impact on bacterial diversity, suggesting that fungi are more sensitive and vulnerable to the bamboo invasion than bacteria. We conclude that native Moso bamboo invasions into subtropical forests may lead to a complex biogeochemical process in the litter–soil system, which may threaten local forest ecosystems by affecting microbial communities and, thus, litter decomposition and nutrient cycling.

Litsea cubeba (Lour.) Pers., a popular essential oil plant, is a dioecious species with degenerative sexual organs in both male and female individuals. Yet, the mechanism of degenerative organs development in male and female flowers is poorly understood. Here, we analyzed the morphological characters of degenerative organ development by morphological and histological observations, and determined the critical stage of abortion that occurs at pre-meiosis in male and female flowers. We also conducted RNA sequencing (RNA-seq) to understand the genetic basis of stamen abortion in female flowers. The differentially expressed genes (DEGs) were identified during the staminode development in female flowers; functional enrichment analysis revealed some important biological pathways involved the regulation of stamen abortion, including plant hormone signal transduction, phenylpropanoid biosynthesis, flavonoid biosynthesis and monoterpenoid biosynthesis. Furthermore, 15 DEGs involved in the hormone pathways were found to regulate stamen development. By HPLC-MS/MS analysis, there were a salicylic acid (SA) content peak and the gibberellin (GA) content lowest point in the abortion processes in female flowers, suggesting a vital function of hormonal processes. Co-expression network analysis further identified several hub genes that potentially played significant roles in the stamen abortion of L. cubeba. Taken together, we proposed a model involved in plant hormones pathways underlying stamen abortion during pre-meiosis in female flowers of L. cubeba.

Camellia nitidissima is famous for its golden flowers. Its flowers are rich in secondary metabolites, and they have ornamental, medicinal, and edible value. Pigment composition and regulation has been studied in the golden petals, but there has been little research on pigment composition or the molecular mechanism underlying yellow stamens in C. nitidissima. To explore the molecular mechanism of yellow stamen formation, three developmental stages (S0, S1, and S2) were used for transcriptome and pigment analyses. Pigment analysis showed that the flavonoid content increased sharply from the S0 to S1 stage and decreased from the S1 to S2 stage, and the carotenoid content increased sharply during yellow stamen formation (from the S1 to S2 stage). RNA-seq analysis showed that a total of 20,483 differentially expressed genes (DEGs) were identified. KEGG and heatmap analyses showed that flavonoid and carotenoid biosynthesis pathways were enriched, and we identified 14 structural genes involved in flavonoid biosynthesis and 13 genes involved in carotenoid biosynthesis and degradation. In addition, the expression of carotenoid- and flavonoid-related genes was consistent with carotenoid and flavonoid content. In addition, correlation network analysis indicated that the WARYK, MYB, bHLH, and AP2/ERF transcription factor families were screened for involvement in the biosynthesis of flavonoids and carotenoids. In this study, we describe the pathway associated with color formation in the stamens of C. nitidissima.

The plant MADS-box transcription factor family is a major regulator of plant flower development and reproduction, and the AGAMOUS-LIKE11/SEEDSTICK (AGL11/STK) subfamily plays conserved functions in the seed development of flowering plants. Camellia japonica is a world-famous ornamental flower, and its seed kernels are rich in highly valuable fatty acids. Seed abortion has been found to be common in C. japonica, but little is known about how it is regulated during seed development. In this study, we performed a genome-wide analysis of the MADS-box gene the in C. japonica genome and identified 126 MADS-box genes. Through gene expression profiling in various tissue types, we revealed the C/D-class MADS-box genes were preferentially expressed in seed-related tissues. We identified the AGL11/STK-like gene, CjSTK, and showed that it contained a typical STK motif and exclusively expressed during seed development. We found a significant increase in the CjSTK expression level in aborted seeds compared with normally developing seeds. Furthermore, overexpression of CjSTK in Arabidopsis thaliana caused shorter pods and smaller seeds. Taken together, we concluded that the fine regulation of the CjSTK expression at different stages of seed development is critical for ovule formation and seed abortion in C. japonica. The present study provides evidence revealing the regulation of seed development in Camellia.

In trees, the annual cycling of active and dormant states in buds is closely regulated by environmental factors, which are of primary significance to their productivity and survival. It has been found that the parallel or convergent evolution of molecular pathways that respond to day length or temperature can lead to the establishment of conserved periodic gene expression patterns. In recent years, it has been shown in many woody plants that change in annual rhythmic patterns of gene expression may underpin the adaptive evolution in forest trees. In this review, we summarize the progress on the molecular mechanisms of seasonal regulation on the processes of shoot growth, bud dormancy, and bud break in response to day length and temperature factors. We focus on seasonal expression patterns of genes involved in dormancy and their associated epigenetic modifications; the seasonal changes in the extent of modifications, such as DNA methylation, histone acetylation, and histone methylation, at dormancy-associated loci have been revealed for their actions on gene regulation. In addition, we provide an outlook on the direction of research on the annual cycle of tree growth under climate change.