Light-Responsive Gene Pathway Drives Purple Pigment Buildup in Pepper

Researchers have identified a gene regulatory pathway that controls how purple peppers build up their signature pigments. In a study published in BMC Plant Biology, the team cloned a NAC-family transcription factor, CaNAC83, from purple-fruited pepper and showed that it acts as a positive regulator of anthocyanin biosynthesis, the process behind the deep purple coloration of the fruit and a contributor to its nutritional value. The work also connected this factor to a light-responsive protein, CaHY5, revealing a two-step regulatory chain that links light signals to pigment production.

The characterization began with expression analysis. Quantitative real-time PCR showed that CaNAC83 is expressed predominantly in pepper fruits and flowers. During early fruit development, its expression levels rose, reaching a peak at 35 days post-anthesis before declining again.

To test that role, the researchers used transient silencing and transient overexpression assays in pepper seedlings and detached fruits. When CaNAC83 was silenced, anthocyanin content dropped and the expression of structural genes in the anthocyanin biosynthetic pathway was down-regulated. The opposite occurred with overexpression: anthocyanin accumulation increased significantly, and the same structural genes were expressed at higher levels.

Because both manipulations were transient, the results demonstrate short-term regulatory effects in the tested tissues rather than permanent changes to the plants' genome. The study then probed the mechanism behind these effects. CaNAC83 was shown to bind directly to the promoters of two structural genes, Ca4CL and CaF3H, and to activate their expression.

Both genes encode enzymes in the anthocyanin biosynthetic pathway, so activating them provides a concrete molecular route by which CaNAC83 promotes pigment accumulation in pepper fruits and leaves. The regulatory chain extends one step further upstream. CaNAC83 was found to be targeted and activated by CaHY5, a light-responsive factor.

This connection fits the established observation that light signals induce anthocyanin synthesis and accumulation, and it supplies a molecular explanation for how that environmental cue is translated into pigment production in pepper: light-responsive CaHY5 activates CaNAC83, which in turn switches on the biosynthetic genes. Taken together, the results establish the CaHY5-CaNAC83 pathway as a positive regulator of anthocyanin biosynthesis in pepper. The findings may offer implications for future purple-pepper molecular breeding, since a defined regulatory module connecting light perception to pigment genes could serve as a target for selecting or engineering varieties with enhanced purple coloration and the associated nutritional value.

As the article is an early-access, peer-reviewed accepted version that may still undergo editorial changes before the final Version of Record, the specific details should be read with that status in mind. The evidence so far rests on transient assays in seedlings and detached fruits, so extending the pathway's role to whole-plant and field contexts remains a task for subsequent work.

Subject of Research: The CaHY5-CaNAC83 regulatory pathway controlling anthocyanin biosynthesis in pepper fruits

Article Title: The CaHY5-CaNAC83 regulatory pathway positively regulates anthocyanin biosynthesis in pepper

Article References: Luo, Z., Li, M., Wang, Y., Wang, X., Jiang, S., Bai, Y., Liu, Y., Xie, Q., Deng, M., & Lv, J. (2026). The CaHY5-CaNAC83 regulatory pathway positively regulates anthocyanin biosynthesis in pepper. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10258-6

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10258-6

Keywords: pepper, anthocyanin, CaNAC83, CaHY5, transcription factor, pigment biosynthesis, gene regulation, molecular breeding, purple fruits, plant genetics, CaHY5-CaNAC83, regulatory