Hydrogen peroxide and the secret of fruit ripening: “Signal transmitters” in plants

Research team led by prof. Qin Guozheng from the Institute of Botany of the Chinese Academy of Sciences discovered a previously unrecognized mechanism by which RNA N6 – methyladenosine (m.⁶A) SlALKBH2 demethylase undergoes reduction-oxidation modification (redox). This change affects its stability and physiological role in regulating the normal ripening of tomato fruit.

In this study published IN Nature plantsresearchers deepened their knowledge about the role of hydrogen peroxide (H₂ABOUT₂), a mild oxidant that acts as a key signaling molecule in controlling many biological processes.

They determined that H₂ABOUT₂-through oxidative modification, it regulates the function of SlALKBH2, which is necessary for the proper ripening of fleshy fruits. This ripening stage is the final phase of fruit development, directly affecting fruit quality and shelf life.

In particular, the researchers showed how H₂ABOUT₂ signaling interacts with RNA methylation modification to regulate plant development in a coordinated manner.

The most common chemical modification in eukaryotic mRNAs is, among others,⁶Methylation. It regulates various biological processes, including mRNA stability and translation efficiency, by modulating mRNA metabolism.

As members of the dioxygenase family, among others:⁶A demethylases, including SlALKBH2, are able to oxidatively reverse, among others,⁶Methylation. This ability raises the question of whether SlALKBH2 itself is subject to oxidative modification like other redox-sensitive proteins.

To test this hypothesis, the researchers transiently expressed the SlALKBH2 gene in Nicotiana benthamiana leaves treated with or without H₂ABOUT₂and then the redox state of SlALKBH2 was monitored.

The results showed a clear sensitivity of SlALKBH2 to H₂ABOUT₂-induced oxidation, resulting in the formation of homodimers in both N. benthamiana leaves and tomato fruits. It is worth noting that exposure to H₂ABOUT₂ has been shown to accelerate the ripening of tomato fruit, which causes the oxidation of SlALKBH2 in the process.

The formation of SlALKBH2 homodimers has been attributed to the involvement of multiple cysteine ​​(Cys) residues, with Cys39 identified as a key site; mutation at this site drastically reduces homodimer formation. Although oxidative modification improved the stability of the SlALKBH2 protein, it did not affect its, among others,⁶Demethylase activity.

Furthermore, researchers identified NADPH-thioredoxin reductase C (SlNTRC) as a protein that interacts with SlALKBH2. They showed that SlNTRC regulates the redox state of SlALKBH2, thus influencing its, among others,⁶Demethylation function in tomatoes.

Stable SlNTRC knockout mutants were then generated in tomato using CRISPR–Cas9-mediated gene editing. The homozygous mutant line experienced significant delays in vegetative growth and an inability to bear fruit.

This study established an association between H₂ABOUT₂ signaling named after⁶Methylation, emphasizing the importance of redox regulation, among others⁶Modifiers in the control of fruit ripening.

Considering the key role of RNA, m⁶Scientists speculate that methylation in various biological processes may play a role in other developmental processes.

Overall, this study not only advances our understanding of the molecular mechanisms underlying fruit ripening but also offers new insights and strategies for improving crop varieties.