Light Stress in Yeasts: Signaling and Responses in Creatures of the Night

Abstract

Living organisms on the surface biosphere are periodically yet consistently exposed to light. The adaptive or protective evolution caused by this source of energy has led to the biological systems present in a large variety of organisms, including fungi. Among fungi, yeasts have developed essential protective responses against the deleterious effects of light. Stress generated by light exposure is propagated through the synthesis of hydrogen peroxide and mediated by regulatory factors that are also involved in the response to other stressors. These have included Msn2/4, Crz1, Yap1, and Mga2, thus suggesting that light stress is a common factor in the yeast environmental response.

Studying the Human Microbiota: Advances in Understanding the Fundamentals, Origin, and Evolution of Biological Timekeeping

“…Yeast cells use a peroxisomal oxidase to convert light into an H 2 O 2 signal that is subsequently detected by Tsa1 and relayed to thioredoxin, which inhibits PKA activity and helps regulate the accumulation of Msn2 in the nucleus [44]. Msn2 is a PKA-regulated transcription factor critical for triggering the expression of stress-responsive genes upon exposure to various environmental signals, including oxidative stress [358,359]. Its deletion disturbs LOC to HOC switching, leading to YMC dysregulation [338,360].…”

“…Sunlight, regarded as the inaugural zeitgeber, shaped early circadian systems well before acute oxidative conditions arose (Figure 4, point 1) [358]. Given that even the most 2.…”

“…Sunlight, regarded as the inaugural zeitgeber, shaped early circadian systems well before acute oxidative conditions arose (Figure 4, point 1) [358]. Given that even the most primitive forms of life had to cope with locally low but consequential aerobic conditions (Figure 4, point 2), metabolic and redox pathways must have naturally co-evolved with ancient timekeeping mechanisms (Figure 5).…”