Materials and methods
Plant materials and growth
conditions
The plant materials were 6-year-old apple trees (‘Fuji’
/T337/Malus robusta Rehd.) growing in the experimental orchard of
the Horticulture College of Northwest A & F University (108°04′ E,
34°16′ N). We collected new shoots (2–3 mm in diameter) near the tips,
fully expanded leaves near buds, flower buds, blooming flowers, and
young fruit, which were immediately frozen in liquid nitrogen and stored
at −80°C for later use.
The ‘Fuji’ plants were grown on MS medium containing 0.1
mg·L−1 indolebutyric acid and 0.6
mg·L−1 6-benzylaminopurine under long-day conditions
(16h-light/8h-dark) at 24°C and were subcultured every 45 days.
Arabidopsis plants were grown under long-day conditions
(16h-light/8h-dark) at 22°C. Tomato plants (‘Ailsa Craig’) were grown
under long-day conditions (16h-light/8h-dark) at 25°C.