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A mutant tree with blushed coloring pattern in fruit skin was found and identified as a bud sport of Malus domestica Borkh. cultivar 'Ralls'. This study was aimed at elucidating the genetic basis of this pattern by a comparison of 'Ralls' (striped red) with this bud sport. These two varieties were grown either under normal sunlight (control group) or the fruits were bagged during development (bagged group) and the bags were removed 1 month before harvesting. Anthocyanin content increased during fruit ripening and was higher in the blushed sport than in 'Ralls', by 57% in the control group and by 73% in the bagged group after bag removal. Correspondingly, in both the varieties transcription of six anthocyanin biosynthetic genes was coordinately up-regulated, concomitant with an increase in levels of transcripts of the regulatory gene, MdMYB1, and in general these levels were higher in the blushed sport than in ''Ralls''. However, there were no significant differences between the two varieties in the nucleotide sequences of the genomic region or coding sequence of MdMYB1; nor in the sequences of cDNAs of the other known transcription factors MdbHLH3 and MdbHLH33. Interestingly, DNA methylation in the promoter region of MdMYB1 was inversely correlated with transcript levels of MdMYB1 and was significantly lower in the blushed sport. Thus, we conclude that DNA methylation plays a role in regulating MdMYB1 expression, which in turn regulates anthocyanin biosynthesis and thereby influences the color pattern of the apples.

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Low temperature is a major stress that severely affects plant development, growth, distribution, and productivity. Here, we examined the function of a 2-oxoglutarate-dependent dioxygenase-encoding gene, SlF3HL , in chilling stress responses in tomato ( Solanum lycopersicum cv. Alisa Craig [AC]). Knockdown (KD) of SlF3HL (through RNA interference) in tomato led to increased sensitivity to chilling stress as indicated by elevated levels of electrolyte leakage, malondialdehyde (MDA) and reactive oxygen species (ROS). In addition, the KD plants had decreased levels of proline and decreased activities of peroxisome and superoxide dismutase. The expression of four cold-responsive genes was substantially reduced in the KD plants. Furthermore, seedling growth was significantly greater in AC or SlF3HL -overexpression plants than in the KD plants under either normal growth conditions with methyl jasmonate (MeJA) or chilling stress conditions. SlF3HL appears to positively regulate JA accumulation and the expression of JA biosynthetic and signaling genes under chilling stress. Together, these results suggest that SlF3HL is a positive regulator of chilling stress tolerance and functions in the chilling stress tolerance pathways, possibly by regulating JA biosynthesis, JA signaling, and ROS levels.

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