Pecan (Carya illinoinensis) is a widely consumed edible woody oil species that is rich in unsaturated fatty acids (FAs) that are beneficial to human health. However, the genes and mechanisms regulating seed oil biosynthesis in pecan are not well understood. Here, we analyzed the expression patterns of genes involved in seed oil biosynthesis in two different varieties of pecan with distinct fruit maturation schedules and oil contents. We cloned the C. illinoinensis WRINKLED 1 (CiWRI1) gene, a homolog of ArabidopsisWRINKLED1 (AtWRI1), which plays a key role in FA synthesis. Overexpressing CiWRI1 restored lipid synthesis in the Arabidopsiswri1-1 mutant and rescued other phenotypic defects such as plant height, root length, and germination rate, suggesting that CiWRI1 is an ortholog of the AtWRI1 and is involved in the regulation of FA synthesis. To investigate the mechanism of CiWRI1 regulation, we cloned C. illinoinensis BIOTIN CARBOXYL CARRIER PROTEIN ISOFORM2 (CiBCCP2) and determined that the CiWRI1 protein directly binds to an ASML1/WRI1 (AW)-box motif in the CiBCCP2 gene promoter and thereby activates its transcription. CiBCCP2 overexpression partly rescued the phenotypic defects of the wri1-1 mutant, indicating that it is directly regulated by CiWRI1. Thus, de novo FA biosynthesis in seed is conserved across plant species; moreover, CiWRI1 regulates oil synthesis by directly controlling CiBCCP2 expression. These findings present novel potential targets for molecular-marker-assisted breeding of this commercially important plant.

Rootstocks are well known to have important effects on scion growth performance. However, the involved mechanisms remain unclear. Recent studies provided some clues on the potential involvement of DNA methylation in grafting, which open up new horizons for exploring how rootstocks induce the growth changes. To better understand the involvement of DNA methylation in rootstock-induced growth alterations, whole-genome bisulfite sequencing (WGBS) was used to evaluate the methylation profiles of two sets of pecan grafts with different growth performances on different sizes of rootstocks. The results showed that methylated cytosines accounted for 24.52%–25.60% of all cytosines in pecan. Methylation levels in CG were the highest, with the lowest levels being in CHH (C= cytosine; G= guanine; H = adenine, thymine, or cytosine). Rootstocks induced extensive methylation alterations in scions with 934, 2864, and 15,789 differentially methylated regions (DMRs) determined in CG, CHG, and CHH contexts, respectively. DMR-related genes (DMGs) were found to participate in various processes associated with plant growth, among which 17 DMGs were found, most likely related to hormone response, that may play particularly important roles in graft growth regulation. This study revealed DNA methylomes throughout the pecan genome for the first time, and obtained abundant genes with methylation alterations that were potentially involved in rootstock-induced growth changes in pecan scions, which lays a good basis for further epigenetic studies on pecan and deeper understanding of grafting mechanisms in pecan grafts.

Chloranthus spicatus is one of the main scented tea varieties cultivated mainly in the Huangshan region, and dried flowers of these plants are mainly used for imparting a characteristic aroma to the tea. However, climatic variations in Huangshan limit its cultivation, with water deficit (WD) being the main limiting factor. The present study evaluated the effects of different WD intensities on the growth and physiological parameters of C. spicatus seedlings to determine the optimal soil moisture content for their large-scale cultivation. The experimental design comprised a control group (95–100%) and three treatment groups, namely mild WD (75–80%), moderate WD (55–60%), and severe WD (35–40%). Each treatment lasted 45 days and was given to 10 potted C. spicatus seedlings, with 3 replicates. Measurements were conducted for the shoot length and diameter; biomass; photosynthesis parameter; activities of antioxidant enzymes, namely superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and soluble protein (SP) and malonylaldehyde (MDA) contents of the seedlings. The results indicated that mild and moderate WD positively affected C. spicatus seedlings in terms of shoot length, diameter, biomass, root/shoot ratio, photosynthesis rate, intercellular CO₂ concentration, water use efficiency, and carboxylation efficiency. Moreover, the growth and photosynthesis were increased in the mild and moderate WD seedlings but decreased in the severe WD seedlings. Mild and moderate WD also led to a significant decrease in the antioxidant enzyme activities and the MDA content of seedlings (p < 0.05), all of which exhibited higher levels in severe WD seedlings. These results indicated that severe water stress restricted the growth of seedlings, while mild and moderate stress proved beneficial. SP content of the seedlings increased under mild and moderate WD but decreased under severe WD. We infer that the strong hydrophilicity of SPs in the seedlings results in the accumulation of water in plant cells, thus conferring resistance to drought stress. In conclusion, reducing the soil moisture content by 55–80% in the Huangshan region may be a promising strategy for boosting its cultivation.