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- Author or Editor: Katsuhiro Shiratake x
Previously, we showed that a reduction of FaTFL2 (homolog of Arabidopsis thaliana TFL1) expression is a key signal for flowering in domesticated octaploid strawberries (Fragaria ×ananassa). Since FaTFL2 expression seemed to be regulated by temperature rather than by photoperiod, we investigated whether down regulation of FaTFL2 and floral meristem generation occurred at different temperature conditions. In addition to the conditions for a normal super-forcing cultivation system of an 8-hour photoperiod and day/night temperatures of 31.2 or 30/15 °C, flowering also was generated under the same photoperiod and day/night temperatures of day/night-half/night-half temperatures of 30/15/25 °C conditions. We demonstrate that the new super-forcing cultivation system is energy saving based on the reduction of FaTFL2 expression.
The regulation of NAD+-dependent sorbitol dehydrogenase (NAD-SDH, EC 1.1.1.14) by sugar was investigated by using sliced tissues of japanese pear (Pyrus serotina Nakai cv. Kousui) fruit in order to determine its role in the mechanism of sugar accumulation in fruit tissue. The results of the activities and steady-state levels of the protein and mRNA indicate that NAD-SDH in japanese pear fruit is among the sugar-inducible genes. By preincubating the sliced tissues for 16 hours in a medium without sugar, NAD-SDH activity declined and reached a stable level that was maintained for up to 40 hours. The washing procedure also reduced the sugar concentration in the apoplast and cytosol of the sliced tissues to low concentrations and enabled them to be manipulated by exogenous applications of carbohydrate solutions. Incubation of tissues in 50 or 100 mm sorbitol for 8 hours led to enhanced expression of the NAD-SDH gene as determined by increased mRNA and protein levels and enhanced enzyme activity. The presence of 100 mm glucose, sucrose, or mannitol also gave significant stimulation on the levels of activity, protein, and mRNA of NAD-SDH compared with those of control tissues bathed in media in which the osmotic potential had been adjusted to that of the sugar solutions by adding polyethylene glycol. However, fructose was ineffective in stimulating NAD-SDH activities and the level of the protein was not enhanced but the level of mRNA was increased. Therefore, it is suggested that NAD-SDH gene transcription is enhanced by each sugar investigated, and fructose appears to be unique as it also influences NAD-SDH at a post-transcriptional level.
We re-investigated the flesh color and S-genotypes of progenies of red-fleshed apple cultivar JPP35, which was produced by ‘Jonathan’ × ‘Pink Pearl’, and clarified that 100% and 96% of progenies from ‘Shinano Sweet’ (S1S7 ) × ‘JPP35’ (S3S7 ) and ‘Orin’ (S2S7 ) × ‘JPP35’ (S3S7 ) containing S3-RNase allele, respectively, showed the red flesh trait. Using this tight linkage between red flesh trait and self- and cross-compatibility relating allele such as S3 -RNase allele, we showed suitable cultivar combinations for efficient production of various red-fleshed apples. We also identified an unknown S-RNase allele in ‘Pink Pearl’ as S11 and determined its partial genomic sequence, including a complete intron with its known S3 -RNase allele.
We have used a red-fleshed apple cultivar, Malus ×domestica Pink Pearl, and its progeny, ‘JPP 35’, as paternal parents for producing new red-fleshed cultivars suitable for fresh use or processing such as pie fillings, dried apple, apple juice, or cider. In this process, we found that the S3 -RNase allele of ‘Pink Pearl’ was linked to its red flesh trait. It was suggested that this trait might be controlled by a new gene apart from the MYB10 (MdMYB10) gene. Using ‘JPP 35’ (S-RNase allele genotype; S3S7 ) produced by ‘Jonathan’ (S7S9 ) × ‘Pink Pearl’ (S3Sx ) as a paternal parent, we developed a system for producing red-fleshed progenies suitable for fresh use. That is, 96% and 86% of progenies from ‘Shinano Sweet’ (S1S7 ) × ‘JPP35’ (S3S7 ) and ‘Orin’ (S2S7 ) × ‘JPP35’ (S3S7 ) containing the S3 -RNase allele, respectively, showed the red flesh trait. Similarly, red-fleshed progenies suitable for apple pie or natural red juice could be produced by ‘Jonathan’ (S7S9 ) × ‘JPP35’ (S3S7 ).
We have succeeded in establishing a virus-induced gene silencing (VIGS) of rose using Apple latent spherical virus (ALSV) vectors. An ALSV infection on rose did not cause any symptoms like those observed on other plant species and grew healthy. We have cloned and sequenced the phytoene desaturase (PDS) gene in wild rose, then used its fragment for silencing the rose internal PDS gene. The silencing phenotypes such as the highly uniform photo-bleached phenotype with PDS inhibitions were observed on the upper leaves of primary shoots and on a secondary shoot of R. rugosa for more than 5 months. ALSV vectors seemed useful for analyzing gene function and for the molecular breeding of rose.