Genome-Wide Identification and Expression Pattern Analysis of BAHD Acyltransferase Family in Taxus mairei.

BAHD acyltransferases are involved in catalyzing and regulating the secondary metabolism in plants. Despite this, the members of BAHD family and their functions have not been reported in the Taxus species. In this study, a total of 123 TwBAHD acyltransferases from Taxus wallichiana var. mairei genome were identified and divided into six clades based on phylogenetic analysis, of which Clade VI contained a Taxus-specific branch of 52 members potentially involved in taxol biosynthesis. Most TwBAHDs from the same clade shared similar conserved motifs and gene structures. Besides the typical conserved motifs within the BAHD family, the YPLAGR motif was also conserved in multiple clades of T. mairei. Moreover, only one pair of tandem duplicate genes was found on chromosome 1, with a Ka/Ks ratio < 1, indicating that the function of duplicate genes did not differentiate significantly. RNA-seq analysis revealed different expression patterns of TwBAHDs in MeJA induction and tissue-specific expression experiments. Several TwBAHD genes in the Taxus-specific branch were highly expressed in different tissues of T. mairei, suggesting an important role in the taxol pathway. This study provides comprehensive information for the TwBAHD gene family and sets up a basis for its potential functions.

Changes in Photosynthetic Characteristics between Green-Leaf Poplar Linn. "2025" and Its Bud-Sporting Colored-Leaf Cultivars.

Colored-leaf poplar is increasingly popular due to its great ornamental values and application prospects. However, the photosynthetic characteristics of these colored-leaf cultivars have not been well understood. In this study, the photosynthetic differences between green-leaf poplar Populus deltoids Linn. "2025" (L2025) and colored-leaf cultivars 'Zhonghong poplar' (ZHP), 'Quanhong poplar' (QHP), and 'Caihong poplar' (CHP) were investigated on several levels, including chloroplast ultrastructure observation, photosynthetic physiological characteristics, and expression analysis of key genes. The results showed that the photosynthetic performance of ZHP was basically consistent with that of L2025, while the ranges of light energy absorption and efficiency of light energy utilization decreased to different degrees in CHP and QHP. A relatively low water use efficiency and high dark respiration rate were observed in QHP, suggesting a relatively weak environmental adaptability. The differences in chloroplast structure in different colored-leaf poplars were further observed by transmission electron microscopy. The disorganization of thylakoid in CHP was considered an important reason, resulting in a significant decrease in chlorophyll content compared with other poplar cultivars. Interestingly, CHP exhibited extremely high photosynthetic electron transport activity and photochemical efficiency, which were conductive to maintaining its relatively high photosynthetic performance. The actual quantum yield of PSII photochemistry of ZHP was basically the same as that of QHP, while the relatively high photosynthetic performance indexes in ZHP suggested a more optimized photosynthetic apparatus, which was crucial for the improvement of photosynthetic efficiency. The differential expressions of a series of key genes in different colored-leaf poplars provided a reasonable explanation for anthocyanin accumulation and specific photosynthetic processes.

Family characteristics, phylogenetic reconstruction, and potential applications of the plant BAHD acyltransferase family.

The BAHD acyltransferase family is a class of proteins in plants that can acylate a variety of primary and specialized secondary metabolites. The typically acylated products have greatly improved stability, lipid solubility, and bioavailability and thus show significant differences in their physicochemical properties and pharmacological activities. Here, we review the protein structure, catalytic mechanism, and phylogenetic reconstruction of plant BAHD acyltransferases to describe their family characteristics, acylation reactions, and the processes of potential functional differentiation. Moreover, the potential applications of the BAHD family in human activities are discussed from the perspectives of improving the quality of economic plants, enhancing the efficacy of medicinal plants, improving plant biomass for use in biofuel, and promoting stress resistance of land plants. This review provides a reference for the research and production of plant BAHD acyltransferases.

Effects of Seasonal Changes on Chlorophyll Fluorescence and Physiological Characteristics in the Two Taxus Species.

Taxus is a rare and endangered woody plant worldwide with important economic and ecological values. However, the weak environmental adaptability of Taxus species, in particular the unstable photosynthetic activity in different seasons, always affects its normal growth and development and limits its conservation and exploitation. To improve the survival of Taxus trees in cultivated areas, the seasonal dynamics of chlorophyll fluorescence (CF) and key physiological parameters were comprehensively investigated in T. media and T. mairei. The results demonstrated that the photosynthetic activity of both Taxus species was sensitive to local summer and winter environmental conditions, with the heterogeneity of fluorescence signatures intuitively presented on the needle surface by CF-Imaging detection, while images of maximum quantum efficiency of PSII photochemistry (Fv/Fm) demonstrated values below 0.7 in the blue-green sectors in winter. The distribution of light energy was regulated by the photosynthetic apparatus in both Taxus species to maintain a stable actual quantum yield of PSII photochemistry (φPSII), which was around 0.4-0.5. Based on a redundancy discriminant analysis, the interpretation rate of light intensity and air temperature ranked as the top two in both Taxus species, which were considered the main environmental factors affecting the photosynthetic performance of Taxus by disturbing the electron transport chain. In the winter, T. mairei exhibited weaker electron transport activity than T. media, thus caused lower photochemistry and more severe photosynthetic damages. Interestingly, both Taxus species demonstrated consistent response patterns, including diverse energy dissipation strategies and enhancement of osmoregulatory substances and antioxidative activities, thus maintaining stable photosynthetic functions in response to environmental changes.