Exploring Peel Color Differences in Red Pomegranates

Jim Crocker
2nd May, 2024

Exploring Peel Color Differences in Red Pomegranates

Image Source: Natural Science News, 2024

Key Findings

  • Study at Nanjing Forestry University found why some pomegranates are red and others purple-red
  • Purple-red 'Moshiliu' pomegranates have higher levels of certain pigments from early growth stages
  • Specific genes and proteins (MYB transcription factors) regulate the color differences in pomegranate skins
Pomegranates have long been celebrated not only for their taste but also for their nutritional value, particularly due to their rich polyphenolic compounds. These compounds, including anthocyanins, are responsible for the vibrant colors of the fruit's skin, ranging from deep reds to purples. The color variation among pomegranate cultivars is not just a matter of aesthetic preference but also indicates differences in nutritional content. However, the underlying biological mechanisms that dictate this color diversity have remained somewhat elusive. A recent study by researchers at Nanjing Forestry University[1] sheds light on this colorful mystery, providing insights that could have implications for both agriculture and nutrition. The study focuses on two pomegranate cultivars: 'Hongbaoshi', which has red skin, and 'Moshiliu', which is characterized by a purple-red skin. By employing both transcriptomic and metabolomic techniques, the researchers aimed to decipher the genetic and metabolic factors contributing to the color differences between these cultivars. They identified 51 different anthocyanins—pigments responsible for the red, purple, and blue hues in plants—in the fruit peels. The findings showed that the purple-red 'Moshiliu' had high levels of cyanidin (Cy) and delphinidin (Dp) anthocyanins from early development stages, which contributed to its distinctive color. Delving into the genetic regulation of these pigments, the study revealed that the expression of genes related to anthocyanin production was lower in the early stages but higher in the later stages of 'Moshiliu' development compared to 'Hongbaoshi'. This suggests a delayed but ultimately stronger activation of the anthocyanin biosynthesis pathway in 'Moshiliu'. One particular gene, ANR, was found to be highly expressed in 'Hongbaoshi' but barely present in 'Moshiliu', indicating its potential role in the red coloration of 'Hongbaoshi'. The study also highlighted the importance of MYB transcription factors, which are proteins that bind to DNA and regulate the activity of genes. Different subgroups (SG) of R2R3-MYB transcription factors showed varied expression patterns between the two cultivars. In 'Moshiliu', three SG5 MYBs were highly expressed, and one SG6 MYB was significantly decreased. This pattern of expression correlates with the cultivar's high anthocyanin content and purple-red skin. In contrast, SG4 MYBs exhibited divergent expression patterns, suggesting a complex regulatory network influencing skin color. The findings from Nanjing Forestry University build upon previous research that has established the role of MYB transcription factors in plant pigment production. For example, studies on apple skin coloration[2] and pomegranate fruit development[3][4] have identified MYB transcription factors as key regulators of anthocyanin biosynthesis. The current research expands on these findings by demonstrating how specific MYB subgroups contribute to the color variations in pomegranate cultivars, enhancing our understanding of the genetic control of fruit coloration. The implications of this research are multifaceted. For consumers, understanding the genetic basis of fruit color could lead to more informed choices about the nutritional properties of different pomegranate cultivars. For breeders and the agricultural industry, the ability to manipulate MYB transcription factors could pave the way for the development of new cultivars with desired color and nutritional profiles. This could potentially align with the goal of promoting a healthier diet through increased consumption of fruit and vegetables, as plant-derived compounds have been linked to health benefits[5]. In conclusion, the study from Nanjing Forestry University provides a deeper understanding of the genetic and biochemical factors that contribute to the color diversity in pomegranates. By uncovering the specific roles of MYB transcription factors and their impact on anthocyanin accumulation, this research not only unravels the complexity behind the hues of pomegranate skins but also opens the door to novel approaches in the cultivation and enhancement of fruit quality.

GeneticsBiochemPlant Science

References

Main Study

1) Comparative transcriptomic and metabolomic profiles reveal fruit peel color variation in two red pomegranate cultivars.

Published 1st May, 2024

Journal: Plant molecular biology

Issue: Vol 114, Issue 3, May 2024

Related Studies

2) Isolation and functional analysis of a MYB transcription factor gene that is a key regulator for the development of red coloration in apple skin.

Journal: Plant & cell physiology, Issue: Vol 48, Issue 7, Jul 2007

3) MYB5-like and bHLH influence flavonoid composition in pomegranate.

https://doi.org/10.1016/j.plantsci.2020.110563

4) A pomegranate (Punica granatum L.) WD40-repeat gene is a functional homologue of Arabidopsis TTG1 and is involved in the regulation of anthocyanin biosynthesis during pomegranate fruit development.

https://doi.org/10.1007/s00425-011-1438-4

5) MYBs Drive Novel Consumer Traits in Fruits and Vegetables.

https://doi.org/10.1016/j.tplants.2018.06.001


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