How Apple's Color and Nutrients Are Controlled by Gene Interactions

Jim Crocker
26th April, 2024

How Apple's Color and Nutrients Are Controlled by Gene Interactions

Image Source: Natural Science News, 2024

Key Findings

  • Study at Qingdao Agricultural University found how proteins control apple color and nutrition
  • Protein MdMYB44 regulates carotenoid production by interacting with genes MdCCD4 and MdCYP97A3
  • This regulation involves a complex that represses gene activity, affecting apple pigment and health benefits
Carotenoids are vital compounds in plants, responsible for their vibrant colors and also serving as antioxidants. These pigments are not just aesthetic; they play a crucial role in photosynthesis and offer nutritional benefits to humans who consume plant-based foods. However, the precise mechanisms that control carotenoid production in plants, particularly in apples, have remained somewhat elusive. A recent study by researchers at Qingdao Agricultural University[1] sheds new light on this process by exploring the role of certain proteins and gene interactions in the regulation of carotenoid biosynthesis in apple fruit. The study focuses on a protein known as MdMYB44, which acts as a transcriptional repressor – a type of protein that can inhibit the expression of genes. In this case, MdMYB44 influences the production of carotenoids by modulating the activity of two genes: MdCCD4 and MdCYP97A3, which are involved in the carotenoid biosynthesis pathway. The researchers discovered that MdMYB44 can enhance the production of certain carotenoids by repressing the expression of MdCCD4, and conversely, it can suppress the levels of lutein, a specific type of carotenoid, by repressing MdCYP97A3. The repression of these genes is mediated through a complex interaction with another protein called TPR1 and involves a process called histone deacetylation. Histones are proteins around which DNA is wrapped, and their acetylation state can influence gene expression. Deacetylation, therefore, typically leads to a repression of gene activity. In the context of carotenoid biosynthesis, the interaction between MdMYB44 and TPR1, facilitated by a specific region on MdMYB44 known as the EAR motif, leads to histone deacetylation and subsequent repression of MdCCD4 and MdCYP97A3. This finding is significant because it identifies a specific molecular cascade – the MdTPR1-MdMYB44 repressive complex – that regulates the production of carotenoids in apple fruit. This adds a new layer of understanding to the complex network of gene regulation involved in plant pigment production, and it ties in with previous studies that have explored various aspects of carotenoid biosynthesis and regulation in plants. For instance, earlier research on the role of MYB transcription factors in kiwifruit[2] showed that these proteins could influence pigment accumulation by activating genes in the carotenoid biosynthetic pathway. The current study builds on this knowledge by demonstrating that MYB transcription factors can also act as repressors in this pathway, thus highlighting the versatile roles these proteins play in plant development and metabolism. Additionally, the study at Qingdao Agricultural University complements findings that have identified potential rate-limiting steps in carotenogenesis in apple[3] and the effects of overexpressing key biosynthetic genes like PSY1[4]. It provides a more detailed picture of how the expression of these genes can be fine-tuned by regulatory proteins like MdMYB44, which, through interactions with co-repressors, can exert precise control over the carotenoid content in apple fruit. Moreover, the research builds on the concept that susceptibility genes can be targeted to confer resistance to plant diseases, as seen in the study of tomato plants' resistance to Fusarium wilt[5]. While the current study does not directly address disease resistance, the manipulation of transcription factors and understanding their broader roles could have implications for developing crops with enhanced stress tolerance, including resistance to pathogens. In conclusion, the research conducted by Qingdao Agricultural University offers valuable insights into the molecular mechanisms regulating carotenoid biosynthesis in apples. By uncovering the role of the MdTPR1-MdMYB44 repressive complex, scientists now have a clearer understanding of how apple coloration and nutritional content can be genetically controlled. This knowledge not only advances our scientific understanding of plant biology but also has potential applications in agriculture, such as breeding apple varieties with improved health benefits or aesthetic qualities.

GeneticsBiochemPlant Science

References

Main Study

1) The MdMYB44-MdTPR1 repressive complex inhibits MdCCD4 and MdCYP97A3 expression through histone deacetylation to regulate carotenoid biosynthesis in apple.

Published 25th April, 2024

https://doi.org/10.1111/tpj.16782

Related Studies

2) A kiwifruit (Actinidia deliciosa) R2R3-MYB transcription factor modulates chlorophyll and carotenoid accumulation.

https://doi.org/10.1111/nph.15362

3) Metabolic and gene expression analysis of apple (Malus x domestica) carotenogenesis.

https://doi.org/10.1093/jxb/ers134

4) Overexpression of PSY1 increases fruit skin and flesh carotenoid content and reveals associated transcription factors in apple (Malus × domestica).

https://doi.org/10.3389/fpls.2022.967143

5) Specific members of the TOPLESS family are susceptibility genes for Fusarium wilt in tomato and Arabidopsis.

https://doi.org/10.1111/pbi.14183


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