No abstract

The nucellar cells of navel orange(Citrus sinensis Osb. var. brasiliensis Tanaka) were successfully cryopreserved by vitrification. In this method, cells were sufficiently dehydrated with highly concentrated cryoprotective solution(PVS2) prior to direct plunge in liquid nitrogen. The PVS2 contains(w/v) 30% glycerol, 15% ethylene glycol and 15% DMSO in Murashige-Tucker medium(MT) containing 0.15 M sucrose. Cells were treated with 60% PVS2 at 25°C for 5 min and then chilled PVS2 at 0°C for 3 min. The cell suspension of about 0.1 ml was loaded in a 0.5 ml transparent plastic straw and directly plunged in liquid nitrogen for 30 min. After rapid warming, the cell suspension was expelled in 2 ml of MT medium containing 1.2 M sucrose. The average rate of survival was about 80%. The vitrified cells regenerated plantlets. This method is very simple and the time required for cryopreservation is only about 10 min.

Temperature and light are important environmental factors that affect flavonoid biosynthesis in grape berry skin. However, the interrelationships between temperature and light effects on flavonoid biosynthesis have not been fully elucidated at the molecular level. Here, we investigated the effects of temperature and light conditions on the biosynthesis of flavonoids (anthocyanins and flavonols) and the expression levels of related genes in an in vitro environmental experiment using detached grape berries. Sufficient anthocyanin accumulation in the grape skin was observed under a low temperature (15 °C) plus light treatment, whereas high temperature (35 °C) or dark treatment severely suppressed anthocyanin accumulation. This indicates that the accumulation of anthocyanins is dependent on both low temperature and light. qRT-PCR analysis showed that the responses of three MYB-related genes (VlMYBA1-3, VlMYBA1-2, and VlMYBA2) to temperature and light differed greatly even though the products of all three genes had the ability to regulate anthocyanin biosynthesis pathway genes. Furthermore, the expression levels of other MYB-related genes and many flavonoid biosynthesis pathway genes were regulated independently by temperature and light. We also found that temperature and light conditions affected the anthocyanin composition in the skin through the regulation of flavonoid biosynthesis pathway genes. Our results suggest that low temperature and light have a synergistic effect on the expression of genes in the flavonoid biosynthesis pathway. These findings provide new information about the relationships between environmental factors and flavonoid accumulation in grape berry skin.

No abstract

No abstract

Proanthocyanidins (PAs) are secondary metabolites that contribute to the protection of the plant and also to the taste of the fruit, mainly through astringency. Persimmon (Diospyros kaki) is unique in being able to accumulate abundant PAs in the fruit flesh. Fruits of the nonastringent (NA)-type mutants lose their ability to produce PA at an early stage of fruit development, while those of the normal astringent (A) type remain rich in PA until fully ripened. The expression of many PA pathway genes was coincidentally terminated in the NA type at an early stage of fruit development. The five genes encoding the Myb transcription factor were isolated from an A-type cultivar (Kuramitsu). One of them, DkMyb4, showed an expression pattern synchronous to that of the PA pathway genes in A-and NA-type fruit flesh. The ectopic expression of DkMyb4 in kiwifruit (Actinidia deliciosa) induced PA biosynthesis but not anthocyanin biosynthesis. The suppression of DkMyb4 in persimmon calluses caused a substantial down-regulation of the PA pathway genes and PA biosynthesis. Furthermore, analysis of the DNA-binding ability of DkMyb4 showed that it directly binds to the MYBCORE cis-motif in the promoters of the some PA pathway genes. All our results indicate that DkMyb4 acts as a regulator of PA biosynthesis in persimmon and, therefore, suggest that the reduction in the DkMyb4 expression causes the NA-type-specific down-regulation of PA biosynthesis and resultant NA trait.

No abstract

No abstract