Organelle DNA degradation contributes to the efficient use of phosphate in seed plants

Mitochondria and chloroplasts (plastids) both harbour extranuclear DNA that originates from the ancestral endosymbiotic bacteria. These organelle DNAs (orgDNAs) encode limited genetic information but are highly abundant, with multiple copies in vegetative tissues, such as mature leaves. Abundant orgDNA constitutes a substantial pool of organic phosphate along with RNA in chloroplasts, which could potentially contribute to phosphate recycling when it is degraded and relocated. However, whether orgDNA is degraded nucleolytically in leaves remains unclear. In this study, we revealed the prevailing mechanism in which organelle exonuclease DPD1 degrades abundant orgDNA during leaf senescence. The DPD1 degradation system is conserved in seed plants and, more remarkably, we found that it was correlated with the efficient use of phosphate when plants were exposed to nutrient-deficient conditions. The loss of DPD1 compromised both the relocation of phosphorus to upper tissues and the response to phosphate starvation, resulting in reduced plant fitness. Our findings highlighted that DNA is also an internal phosphate-rich reservoir retained in organelles since their endosymbiotic origin

Structural basis for VIPP1 oligomerization and maintenance of thylakoid membrane integrity

Vesicle-inducing protein in plastids 1 (VIPP1) is essential for the biogenesis and maintenance of thylakoid membranes, which transform light into life. However, it is unknown how VIPP1 performs its vital membrane-remodeling functions. Here, we use cryo-electron microscopy to determine structures of cyanobacterial VIPP1 rings, revealing how VIPP1 monomers flex and interweave to form basket-like assemblies of different symmetries. Three VIPP1 monomers together coordinate a non-canonical nucleotide binding pocket on one end of the ring. Inside the ring's lumen, amphipathic helices from each monomer align to form large hydrophobic columns, enabling VIPP1 to bind and curve membranes. In vivo mutations in these hydrophobic surfaces cause extreme thylakoid swelling under high light, indicating an essential role of VIPP1 lipid binding in resisting stress-induced damage. Using cryo-correlative light and electron microscopy (cryo-CLEM), we observe oligomeric VIPP1 coats encapsulating membrane tubules within the Chlamydomonas chloroplast. Our work provides a structural foundation for understanding how VIPP1 directs thylakoid biogenesis and maintenance

においの快・不快が生理反応に及ぼす影響

近年、日常的に使用する生活用品の多くに香りが付与され、香りは日常生活において欠かすことのできない存在となりつつある。本研究では、ストレス負荷の状態において、快適と感じるにおいがリラックス効果をもたらし、生理反応にまで影響を及ぼすのかを解明することを目的とし、快適な環境で香りを嗅いだ時のリラックス状態を脳波測定により観察する実験Ａと、暑熱環境で汗をかいている不快な状態で香りを嗅いだ時の生体反応を観察する実験Ｂを行なった。実験Ａでは、グレープフルーツのにおい付与時にα波出現率が増加し、イソ吉草酸付与時には減少したことから、グレープフルーツを嗅ぐことによりリラックス効果があることが確認できた。実験Ｂでは暑熱環境下で騒音負荷中ににおいを嗅ぐと、多量発汗グループにおいて、グレープフルーツの方がイソ吉草酸よりも有意に発汗量が減少し、発汗抑制が認められた。本研究結果から、不快な状態でグレープフルーツのにおいを嗅ぐことは、心理的にも生理的にもストレスや不快感を緩和する効果があることが示唆された

ストレス蛋白 (HSP 70) が運動による筋損傷・筋疲労の修復に及ぼす影響

Current interest is attracted to the problem on the correlation between physical exercise and heat shock induced protein (HSP 70), especially on the enhanced postischemic myocardial recovery following exercise induction of HSP 70. From the recent papers, the inducible isoform of the 70kDa heat shock protein (HSP) family, HSP 70kDa has been confirmed to protect cells from protein-damaging stressors and has been associated with not only myocardial protection but also recovery of several tissue damages. In the present review article, therefore, the related papers to exercise induced body hyperthermia, muscular damage and HSP 70 family, and their protection and/or recovery mechanism were collected and analyzed from the view-points of biological functions of stress protein HSP 70 family as well as of Granyl-Granyl Acetone (GGA) the HSP inducer

水分補給による持久性運動パフォーマンスの修飾 : 特に水分量・グルコース・電解質の相互関係

Considerable interest is attracted to the problems on water ingestion during exercise, however, it is still hypothesis that water ingestion would attenuate the exercise-induced increase in thermoregulatory mechanism such as rectal and muscle temperatures and plasma epinephrine, thereby resulting in less net muscle glycogen utilization. In the present review article, therefore, the hypothesis was discussed and confirmed by the results of 25 important papers related to the problems of improvement of physical performance based on the following three papers : (1) Effects of fluid ingestion during intermittent high intensity swimming exercise on thermoregulatory response and performance. (2) Effect of fluid ingestion on muscle metabolism during prolonged exercise. (3) Heat stress increases muscle glycogen use but reduces the oxidation of ingested carbohydrates during exercise. These review articles indicate that fluid ingestions reduces muscle glycogen use during prolonged exercise, which may account in part, for the improved performance in the hypothesis mentioned above