彦坂 晶子

The transgenic everbearing strawberry (Fragaria×ananassa Duch. ‘HS 138’) can be cultivated in a closed plant production system to produce functional proteins that enhance human immune functions. In this study, we investigated the effects of light quality on fruit growth and the concentration of human adiponectin (hAdi) at three mature stages in transgenic strawberry. hAdi plants were exposed to 3 different light qualities (white [W], blue [B], and red [R]) for a 16-h light period under fluorescent lamps during the flowering and harvest stage; fruits were then harvested at three different mature stages (small green, turning white, and mature red). hAdi concentration increased with fruit maturation, and the mature red stage fruit from the R light treatment group had a significantly greater concentration of hAdi on a fresh-weight basis than all other treatments. There was no relationship between hAdi concentration and fruit fresh weight and the number of days from anthesis to harvest. Although the factors that promoted the production of the functional hAdi proteins were not clear in this study, the results suggest that the fruit growth stages of the transgenic strawberry differed in their response to light quality. For hAdi plants, exposure to red light resulted in the greatest level of functional protein production under the tested treatments.

The effects of defoliation timing on fruit growth and abortion were monitored in gynoecious, parthenocarpic ‘NK×AN8’ cucumber. In control, non-defoliated plants, fruit attained marketable size at 14 days after anthesis (DAA), whereas some of the fruit from the plants (leaf-to-fruit ratio=2) defoliated at different time points were either stunted or aborted. Stunted and aborted fruit ceased to grow at about 7–8 DAA and at 4 DAA, respectively. When plants were defoliated at 4 DAA or earlier, more than 20% of the fruit aborted, whereas no fruit aborted when defoliated at 6 DAA or later. For fruits neither aborted nor stunted, the relative growth rate (RGR) of a fruit was almost the same for the period between 8 and 14 DAA irrespective of defoliation timing. In plants defoliated at 0 to 8 DAA, however, RGR decreased temporarily after defoliation. These results suggested that sufficient amount of photoassimilates should be continuously transported into fruits up to 4 DAA and 7–8 DAA in order to prevent fruit abortion and stunting, respectively.

21世紀に突入し人類の人口増大はとどまるところを知らず、2050年までには90億人に達すると予測されている。しかしながら耕作地面積は限られており、植物工場のような屋内生産型の食糧供給法の発展が期待される。屋内生産型、特に閉鎖系温室での植物栽培では、照明装置が作物の収量に大きく関わる。そこで本研究では光質と光強度の制御が容易なLEDを利用しトマト果実の転流機構に関する知見を得るため、次世代シークエンサも取り入れた包括的転写・代謝プロファイリングによる統合アプローチを行った。具体的には栽培種トマト（麗容）に予備実験で最適な光質と判断した赤色LEDを2段階の光強度（弱光および強光）で照射し、1週間および2週間生育した。生育後、各時刻点における葉サンプルを収穫した。なお、LEDを全く照射しない植物体も生育し葉サンプルを収穫した。果房については、収穫が可能であった2週間目の植物体を中心に収穫した。果実の湿重量と光強度の関係を調べたところ、光強度が強い条件下で生育したトマトの果実は弱光条件下で収穫したものを比較して、重量が増大した。次世代シークエンサおよびマイクロアレイによる転写プロファイリングは葉4点、果房2点の合計6実験区からのサンプルを使用した。マイクロアレイによる転写プロファイルに関しては現在解析中である。代謝物プロファイリングに関しては、収穫したサンプル全点について行う予定である。