In this study, we performed an association analysis of metabolomics and transcriptomics to reveal the anthocyanin biosynthesis mechanism in a new purple-leaf tea cultivar Zikui (Camellia sinensis cv. Zikui) (ZK). Three glycosylated anthocyanins were identified, including petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside, and their contents were the highest in ZK leaves at 15 days. This is the first report on petunidin 3-O-glucoside in purple-leaf tea. Integrated analysis of the transcriptome and metabolome identified eleven dependent transcription factors, among which CsMYB90 had strong correlations with petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside (PCC > 0.8). Furthermore, we also identified key correlated structural genes, including two positively correlated F3’H (flavonoid-3′-hydroxylase) genes, two positively correlated ANS (anthocyanin synthase) genes, and three negatively correlated PPO (polyphenol oxidase) genes. Overexpression of CsMYB90 in tobacco resulted in dark-purple transgenic calluses. These results showed that the increased accumulation of three anthocyanins in ZK may promote purple-leaf coloration because of changes in the expression levels of genes, including CsMYB90, F3’Hs, ANSs, and PPOs. These findings reveal new insight into the molecular mechanism of anthocyanin biosynthesis in purple-leaf tea plants and provide a series of candidate genes for the breeding of anthocyanin-rich cultivars.

Plasma membrane intrinsic protein (PIP) is one of the largest subfamilies of Aquaporins (AQPs) and plays an important role in plant growth and development, and resistance to abiotic stress. In this study, the full length of the EuPIP1;1 cDNA was cloned from Eucommia ulmoides using the rapid amplification of cDNA ends (RACE) method. The EuPIP1;1 gene was induced by drought treatment and expressed in all tested tissues, with the highest expression level in fruit. The subcellular localization showed that EuPIP1;1 was located in the plasma membrane. Constitutive overexpression of EuPIP1;1 in Arabidopsisthaliana could promote leaf growth and development, and accelerate bolting and flowering. Six genes related to growth and flowering (AtPIF4, AtTCP14, AtCRY1, AtCRY2, AtFCA and AtFT) were significantly up-regulated in transgenic lines. Further, EuPIP1;1 gene improved resistance to drought and salt stress in transgenic Arabidopsis. Under drought and salt stress treatment, the transgenic lines had a higher germination rate and accumulation of osmotic substances, lower membrane damage, and could maintain ion homeostasis. Our results suggest that EuPIP1;1 plays an essential role in plant growth and development and in the response to drought and salt stress.

Growth-regulating factors (GRFs) are plant-specific transcription factors that play an important role in plant growth and development. In this study, fifteen GRF gene members containing QLQ and WRC domains were identified in Zanthoxylum armatum. Phylogenetic and collinearity analysis showed that ZaGRFs were closely related to CsGRFs and AtGRFs, and distantly related to OsGRFs. There are a large number of cis-acting elements related to hormone response and stress induction in the GRF gene promoter region of Z. armatum. Tissue-specific expression analysis showed that except for ZaGRF7, all the ZaGRFs were highly expressed in young parts with active growth and development, including terminal buds, seeds, and young flowers, suggesting their key roles in Z. armatum growth and development. Eight ZaGRFs were selected to investigate the transcriptional response to auxin, gibberellin and drought treatments. A total of six ZaGRFs in the NAA treatment, four ZaGRFs in the GA₃ treatment, and six ZaGRFs in the PEG treatment were induced and significantly up-regulated. Overexpression of ZaGRF6 increased branching and chlorophyll content and delayed senescence of transgenic Nicotiana benthamiana. ZaGRF6 increased the expression of CRF2 and suppressed the expression of ARR4 and CKX1, indicating that ZaGRF6 is involved in cytokinin metabolism and signal transduction. These research results lay a foundation for further analysis of the GRF gene function of Z. armatum and provide candidate genes for growth, development, and stress resistance breeding of Z. armatum.

Aquaporins are a specific type of membrane channel proteins that efficiently transport water molecules and other small molecular substrates in plants. In this study, we isolated the plasma membrane aquaporin gene EuPIP1;2 from Eucommia ulmoides, an important medicinal plant in China. The EuPIP1;2 protein was localized on the plasma membrane. Quantitative RT-PCR analysis revealed that EuPIP1;2 was constitutively expressed in all analyzed tissues, with the highest expression levels detected in the fruit and root. Overexpression of EuPIP1;2 in transgenic tobacco enhanced plant tolerance of drought and salinity. Under drought and salt stress, the transgenic lines exhibited higher percentage germination, longer roots, and enhanced percentage survival compared with wild-type plants. The contents of malonaldehyde and proline suggested that EuPIP1;2 improved drought and salt tolerance in transgenic lines by reducing damage to membranes and improving osmotic adjustment. We predict that EuPIP1;2 could be applied to improve drought and salt tolerance in transgenic plants.

Lodging resistance of rice (Oryza sativa L.) has always been a hot issue in agricultural production. A brittle stem mutant, osbc17, was identified by screening an EMS (Ethylmethane sulfonate) mutant library established in our laboratory. The stem segments and leaves of the mutant were obviously brittle and fragile, with low mechanical strength. Examination of paraffin sections of flag leaf and internode samples indicated that the number of cell layers in mechanical tissue of the mutant was decreased compared with the wild type, Pingtangheinuo, and scanning electron microscopy revealed that the mechanical tissue cell walls of the mutant were thinner. Lignin contents of the internodes of mature-stage rice were significantly lower in the mutant than in the wild type. By the MutMap method, we found candidate gene OsBC17, which was located on rice chromosome 2 and had a 2433 bp long coding sequence encoding a protein sequence of 810 amino acid residues with unknown function. According to LC-MS/MS analysis of intermediate products of the lignin synthesis pathway, the accumulation of caffeyl alcohol in the osbc17 mutant was significantly higher than in Pingtangheinuo. Caffeyl alcohol can be polymerized to the catechyl lignin monomer by laccase ChLAC8; however, ChLAC8 and OsBC17 are not homologous proteins, which suggests that the osbc17 gene is involved in this process by regulating laccase expression.