Pecan (Carya illinoinensis) is sensitive to Zn, which is involved in basic physiological and biochemical processes.• To explore the growth and physiology of pecan in response to Zn application, we used 1-year-old annual grafted seedlings (Pawnee) and applied four concentrations of Zn fertilizer (0.05, 0.10, 0.20 and 0.40 gÁplant À1 ); a control (CK; no Zn fertilization) was also included. The growth characteristics, anatomical structure of the leaves and photosynthesis were assessed.• Compared with the CK, photosynthesis and chlorophyll (Chl) fluorescence parameters, leaf area and leaf structure significantly increased at Zn concentrations of 0.05 and 0.10 gÁplant À1 . In addition, growth of pecan at the seedling stage increased in response to moderate Zn application. In contrast, treatment with 0.20 and 0.40 gÁZnÁplant À1 dramatically decreased these physiological indices and inhibited pecan growth.• The results show that moderate soil Zn application promotes pecan growth and development by increasing photosynthesis. However excess Zn concentrations were not conducive to seedling growth. The concentration of 0.1 gÁZnÁplant À1 was best when considering long-term soil Zn applications, providing a theoretical foundation for microelement management of pecan.

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.

No abstract