Tiejin Ying

Ultrastructure characteristics and quality changes of low-moisture Chilgoza pine nut (Pinus gerardiana) during the near-freezing-temperature storage

ABSTRACT The effects of thermal treatment on the ultrastructure and quality of Chilgoza pine nuts stored at near-freezing temperature were investigated. The moisture content of pine nuts was adjusted to 13.3%, compared to the initial 17.3% moisture content. Thermal treatment improved the storage stability. The hydrolysis of lipids was delayed in low-moisture pine nuts, resulting in a significant inhibition of free fatty acid accumulation in pine nuts. Low-moisture pine nuts also showed lower peroxide and thiobarbituric acid (TBA) values compared with the control. Ultrastructure characterization revealed that thermal treatment maintained the cell integrity, deferred the degradation of the plasmalemma and protected the internal lipid droplet. Thermal treatment better retained the antioxidant components, including total phenolics and vitamin E, and reduced the activities of lipase and lipoxygenase in pine nuts. These results indicated that thermal treatment could retard the senescence and deterioration of quality in pine nuts stored at a near-freezing temperature.

SlAREB1 transcriptional activation of NOR is involved in abscisic acid-modulated ethylene biosynthesis during tomato fruit ripening

Many studies have shown that abscisic acid (ABA) regulates climacteric fruits ripening by inducing ethylene production. Nevertheless, the key components involved in the crosstalk between these two phytohormones in controlling fruit ripening remain unknown. SlAREB1, a downstream transcription factor in ABA signaling pathway, has been reported to mediate ABA signaling that regulates tomato ripening through induction of ethylene biosynthetic genes. NOR, a member of NAC domain family, was proved to act upstream of ethylene and essential for ripening- and ethylene-associated genes expression. Here, we found that the expression of SlAREB1 and NOR are both ABA-inducible, and SlAREB1 transcription reaches the peak level prior to NOR during the ripening process. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and dual luciferase assay indicated NOR as a novel direct target of SlAREB1. Transient over-expression of SlAREB1 in tomato fruits results in elevated expression of NOR as well as a number of downstream ethylene biosynthetic genes including SlACS2, SlACS4 and SlACO1, suggesting that SlAREB1 can mediate ABA signal to activate NOR transcription and ultimately promote ethylene synthesis. Based on these data, we present a model suggesting that the SlAREB1-NOR regulation is a crucial node modulating ABA-regulated ethylene biosynthesis during tomato fruit ripening.

Contribution of abscisic acid to aromatic volatiles in cherry tomato (Solanum lycopersicum L.) fruit during postharvest ripening

Fruit aroma development depends on ripening. Abscisic acid (ABA) has been reported to be involved in the regulation of tomato fruit ripening. In the present study, the effects of exogenous ABA on aromatic volatiles in tomato fruit during postharvest ripening were studied. The results showed that exogenous ABA accelerated color development and ethylene production as well as the accumulation of carotenoids, total phenolics and linoleic acid in tomato fruit during ripening. Moreover, exogenous ABA increased the accumulation of volatile compounds such as 1-peten-3-one (2.06-fold), β-damascenone (1.64-fold), benzaldehyde (3.29-fold) and benzyl cyanide (4.15-fold); induced the expression of key genes implicated in the biosynthesis pathways of aromatic volatiles, including TomloxC, HPL, ADH2, LeCCD1B and SlBCAT1 (the values of the log2 fold changes ranged from -3.02 to 2.97); and promoted the activities of lipoxygenase (LOX), hydroperoxide lyase (HPL) and alcohol dehydrogenase (ADH). In addition, the results of promoter analyses revealed that cis-acting elements involved in ABA responsiveness (ABREs) exist in 8 of the 12 key genes involved in volatile biosynthesis, suggesting that ABA potentially affects aromatic volatile emissions via the regulation of gene expression profiles.