Aldh2 dependent formaldehyde metabolism fuels purine demands in melanocyte stem cells

ABSTRACTAldehyde-processing enzymes are viewed as essential clearing agents that rapidly deactivate harmful aldehydes. In the bone marrow, two specific enzymes, aldehyde dehydrogenase (ALDH) 2 and alcohol dehydrogenase (ADH) 5, were previously reported to protect hematopoietic stem cells from endogenous formaldehyde accumulation. Unexpectedly, we found that melanocyte stem cells (McSCs) in zebrafish depend on formate, an Aldh2-generated reaction product, to drive regeneration. Activated McSCs require Aldh2 (but not Adh5) to generate differentiated progeny, and by using scRNA-sequencing analysis, we identified a de novo purine biosynthesis program that is uniquely present in activated McSCs. Consistent with formate serving as one-carbon units for nucleotide biosynthesis, we found that purine supplementation (but not pyrimidine supplementation) was able to restore melanocyte regeneration in the absence of Aldh2. This work shows that Aldh2 enzymes generate reaction products that are needed to meet metabolic demands in regeneration.

Efficiency of Volatile Formaldehyde Removal by Indoor Plants: Contribution of Aerial Plant Parts versus the Root Zone

The contribution of aerial plant parts versus the root zone to the removal of volatile formaldehyde by potted Fatsia japonica Decne. & Planch. and Ficus benjamina L. plants was assessed during the day and night. The removal capacity of the entire plant, aerial plant parts, and root zone was determined by exposing the relevant parts to gaseous formaldehyde (2 μL·L−1) in airtight chambers (1.0 m3) constructed of inert materials. The rate of formaldehyde removal was initially rapid but decreased as the internal concentration diminished in the chamber. To compare the removal efficiency between species and plant parts, the time interval required to reach 50% of the initial concentration was determined (96 and 123 min for entire plants of F. japonica and F. benjamina, respectively). In both species, the aerial plant parts reduced the formaldehyde concentration during the day but removed little during the night. However, the root zone eliminated a substantial amount of formaldehyde during the day and night. The ratio of formaldehyde removal by aerial plant parts versus the root zone was similar for both species, at ≈1:1 during the day and 1:11 at night. The effectiveness of the root zone in formaldehyde removal was due primarily to microorganisms and roots (≈90%); only about 10% was due to adsorption by the growing medium. The results indicate that the root zone is a major contributor to the removal of formaldehyde. A better understanding of formaldehyde metabolism by root zone microflora should facilitate maximizing the phytoremediation efficiency of indoor plants.