Temporal metabolic coordination of UV-resistance system via the circadian clock

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K19349
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 44:Biology at cellular to organismal levels, and related fields
• Research Institution: Waseda University
• Principal Investigator: Iwasaki Hideo 早稲田大学, 理工学術院, 教授 (00324393)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: シアノバクテリア / UV耐性 / kaiABC / グリコゲン代謝 / 概日リズム / Synechococcus

Outline of Final Research Achievements

Circadian control of UV resistance has been reported in several eukaryotic organisms, from algae to higher organisms, although the underlying mechanisms remain unknown. Here, we demonstrate that the unicellular cyanobacterium Synechococcus elongatus PCC 7942 exhibits a circadian rhythm in resistance to UV-C and UV-B light, which is higher during subjective dawn and lower during subjective dusk. Nullification of the clock gene cluster kaiABC or the DNA-photolyase phr abolished rhythmicity with constitutively lower resistance to UV-C light, and amino acid substitutions of KaiC altered the period lengths of the UV-C resistance rhythm. Based on further experiments, we showed that UV-C resistance is weakened by directing more metabolic flux to the glycogen catabolic pathway. Thus, glycogen and its downstream energy metabolism likely affect the circadian control of UV-C resistance through unknown mechanism(s).

Free Research Field

時間生物学

Academic Significance and Societal Importance of the Research Achievements

UV耐性の概日リズムは、その重要性が指摘されていながらも報告例は少なく、具体的な分子機構は明らかになってきませんでした。今回、細胞内のエネルギーフロー（グリコゲン代謝）とUV耐性にトレードオフが見出されたことは、UV耐性の獲得には相当な負荷がかかること、それ故に常にUV耐性を高い状態で維持するよりも、高い時刻と低い時刻を時間的に分業することでエネルギーの消耗を避けていると考えられるようになりました。これらの知見は、概日システムの進化やUV耐性リズムの合理性を考えるうえで重要な知見と考えられます。