Camellia fruit is a woody edible oil source with a recalcitrant pericarp, which increases processing costs. However, the relevance of pericarp thickness variations in Camellia species remains unclear. Therefore, this study aimed to identify pericarp differences at the metabolic and transcription levels between thick-pericarp Camellia drupifera BG and thin-pericarp Camellia oleifera SG. Forty differentially accumulated metabolites were screened through non-targeted UHPLC-Q-TOF MS-based metabolite profiling. S-lignin was prominently upregulated in BG compared with SG, contributing to the thick pericarp of BG. KEGG enrichment and coexpression network analysis showed 29 differentially expressed genes associated with the lignin biosynthetic pathway, including 21 genes encoding catalysts and 8 encoding transcription factors. Nine upregulated genes encoding catalysts potentially led to S-lignin accumulation in BG pericarp, and transcription factors NAC and MYB were possibly involved in major transcriptional regulatory mechanisms. Conventional growth-related factors WRKYs and AP2/ERFs were positively associated while pathogenesis-related proteins MLP328 and NCS2 were negatively associated with S-lignin content. Thus, Camellia balances growth and defense possibly by altering lignin biosynthesis. The results of this study may guide the genetic modifications of C. drupifera to optimize its growth–defense balance and improve seed accessibility.

Virus-induced gene silencing (VIGS) is a rapid and powerful method for gene functional analysis in plants that pose challenges in stable transformation. Numerous VIGS systems based on Agrobacterium infiltration has been widely developed for tender tissues of various plant species, yet none is available for recalcitrant perennial woody plants with firmly lignified capsules, such as tea oil camellia. Therefore, there is an urgent need for an efficient, robust, and cost-effective VIGS system for recalcitrant tissues. Herein, we initiated the Tobacco rattle virus (TRV)-elicited VIGS in Camellia drupifera capsules with an orthogonal analysis including three factors: silencing target, virus inoculation approach, and capsule developmental stage. To facilitate observation and statistical analysis, two genes predominantly involved in pericarp pigmentation were selected for silencing efficiency: CdCRY1 (coding for a key photoreceptor affecting light-responsive perceivable anthocyanin accumulation in exocarps) and CdLAC15 (coding for an oxidase catalyzing the oxidative polymerization of proanthocyanidins in mesocarps, resulting in unperceivable red-hued mesocarps). The infiltration efficiency achieved for each gene was ~ 93.94% by pericarp cutting immersion. The optimal VIGS effect for each gene was observed at early (~ 69.80% for CdCRY1) and mid stages (~ 90.91% for CdLAC15) of capsule development. Using our optimized VIGS system, CdCRY1 and CdLAC15 expression was successfully knocked down in Camellia drupifera pericarps, leading to fading phenotypes in exocarps and mesocarps, respectively. The established VIGS system may facilitate functional genomic studies in tea oil camellia and other recalcitrant fruits of woody plants.

Plants can be grouped into sun- and shade-type owing to their distinct irradiance adaptation. Aglaonema commutatum is a typical shade-tolerant perennial foliage plant native to South Asia with various leaf colorations. ‘Red’ cultivars are widely used for interior decorations and as courtyard ornamental plants, owing to their unique hue and bi-adaptation of both low and high irradiance. However, the underlying source of ‘red’ pigment-dependent irradiance bi-adaptation remains largely unknown. Therefore, four A. commutatum cultivars were comparatively evaluated in terms of pigment composition and photosynthetic rate under full light (sunlight) or 50% full light (shade) to unveil the relationship between pigmentation and irradiance bi-adaptation. Our results showed that the photosynthetic rate of sun leaves generated from light response curves was significantly correlated with anthocyanin content and chlorophyll in red cultivars, suggesting the influence of anthocyanin–light interactions on the high/low irradiance bi-adaptation of red A. commutatum. This study provides a theoretical basis for further cultivating red foliage A. commutatum cultivars under diverse light conditions.

Background: Adinandra nitida, commonly known as Shiya tea, is a healthcare drink enriched in several phenolic acids and flavonoids, with a purple-red leaf variety possessing a unique flavor and a higher economic value. However, the mechanisms underlying leaf coloration and senescence discoloration remain unknown. Methods: Here, we compared both varieties of A. nitida (purple-red leaf, RL, and green leaf, GL) at two stages of development. To make sure the difference in leaf color in these four groups, several indexes, leaf colorimetric differences, H2O2 content in leaf cells, and antioxidant enzymes activities (superoxide dismutase (SOD), catalase (CAT)) were measured. With the integration of metabolome and transcriptome becoming a trend, metabolites in four groups were detected using an Ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) system, and the transcriptome was performed after the extraction of RNA in samples. Afterward, the activities of laccase (LAC) and peroxidase (POD) were measured for further analysis. Results: The deeper or discoloration of leaf color was not caused by the reactive oxygen species (ROS) stress because the H2O2 content was similar for each group. And the SOD and CAT activities improved significantly in young leaves, especially RL_young. Metabolome data showed a large shift in four groups. By focusing on the variation of flavonoids and 1079 metabolites detected in both varieties, along with the accumulation of flavonoids and tannins, proanthocyanins (PAs) were mostly accumulated in young RL. Differential analysis of expressed genes (DEGs) revealed six genes associated with leaf discoloration as hub factors, of which ANRs (ANR1 and ANR2) were positively correlated with the accumulation of PA in RL. Conclusions: Using integrate analysis of metabolome and transcriptome, our results revealed that six structural genes found in proanthocyanin biosynthesis, two reductases (ANR), two oxidative polymerases (POD64, LAC17) and two TFs (bHLH3 and MYB4) related to biosynthesis and polymerization of proanthocyanins were associated with not only the difference of GL and RL but also the faded coloration in two RL groups (RL_young and RL_old), which provided a foundation for further research on an understanding of the regulatory genes and the enzymes specific for proanthocyanidin biosynthesis, facilitating the genetic engineering of crops for beneficial metabolite accumulation.

The drought stress responses of plants are complex regulatory mechanisms that include various physiological responses reflected by the global metabolic status. Metabolomics is an effective, analytical, and instrumental technique for informatics/statistics for the acquisition of comprehensive information on metabolites. We investigate the effect of drought stress on a Belosynapsis ciliata cultivar, ‘Qiuhong’ (a drought-tolerant cultivar), using liquid chromatography-mass spectrometry based on a widely targeted metabolomic approach. ‘Qiuhong’ leaves are subjected to 15- and 30-day drought treatments and are then compared to a control group without drought stress and a rehydration group. In total, 290 differentially accumulated metabolites were detected between drought and normal conditions through multivariate statistical analyses, of which 65 metabolites (36 upregulated and 29 downregulated) were highlighted for their significant contribution to drought tolerance, including an anthocyanin (peonidin 3-O-galactoside) that caused the purple-red hue in leaves under drought stress. In addition, we found that two significantly altered pathways (citrate cycle and purine metabolism) were related to enhanced drought tolerance in plants. Notably, the synthesis of three compounds (p-coumaroyl putrescine, apigenin 6-C-glucoside, and β-nicotinamide mononucleotide) was specifically induced in the drought-treated ‘Qiuhong’, indicating their critical roles in drought resistance. Our results provide a foundation for further research on drought-resistant mechanisms in B. ciliata.

Mikania micrantha (Asteraceae) is an invasive vine found in tropical and southern subtropical Asian and the Pacific Islands. The current methods used to control this vine are inadequate, which warrants the development of ecologically sustainable methods. Therefore, we investigated the ability of four grass species to prevent the invasion of M. micrantha, with an ultimate goal of developing ecologically sustainable control methods for widespread application. The clumps of native grass species from China (Panicum incomtum, Pennisetum purpureum, Saccharum arundinaceum and Microstegium vagans) were established. We sowed M. micrantha seeds and transplanted the seedlings into the grass clumps to examine whether the clumps could eliminate the new M. micrantha plants. In addition, we transplanted M. micrantha into existing grass clumps to examine whether the grass clumps could prevent the re-invasion of M. micrantha. Furthermore, we grew M. micrantha with P. incomtum and P. purpureum in the field to examine whether the grasses could outcompete M. micrantha. Mikania micrantha seeds germinated hardly in the grass clumps, and all seedlings died within 3 months. It was difficult for the vine to survive in the grass clumps. Our field experiments showed that the coverage of M. micrantha was significantly lower than that of the grass species in the first year, and that the vine was outcompeted after 2 years. To the best of our knowledge, this study is the first to reveal that tall grasses, particularly P. incomtum and P. purpureum, have potential to serve as bio-control agents for M. micrantha.