Unlocking the Secrets of Purple Leaf Colors in Mulberry Plants

Jenn Hoskins
24th January, 2024

Unlocking the Secrets of Purple Leaf Colors in Mulberry Plants

A white mulberry (Morus alba) genotype shown from study which develops unique purplish-red young leaves that turn green as they mature (from left to right), eventually becoming indistinguishable from the leaves of a standard green variety.

Image adapted from: Li et al. / CC BY (Source)
Leaf color in plants is often due to pigments, particularly anthocyanins, and is important for both the plant itself and for human uses like food coloring and medicine. Despite this, the exact biological processes that control leaf color development aren’t fully understood. Researchers at Southwest University[1] recently investigated this in mulberry trees, focusing on why some varieties have purplish-red young leaves while others remain green. The study compared two closely related mulberry types: one with purplish-red leaves (EP) and one with normal green leaves (EW). To understand the differences, the researchers used two main techniques: transcriptomics and metabolomics. Transcriptomics examines all the RNA molecules in a cell, providing a snapshot of which genes are active. Metabolomics identifies and measures all the small molecules (metabolites) present, giving insight into the biochemical processes happening within the plant. The results showed a strong link between leaf color and the presence of specific anthocyanins, particularly delphinidin-3-O-glucoside. This type of anthocyanin is responsible for red and purple hues[2]. The purplish-red leaves had significantly higher levels of this compound. The researchers also found that certain genes involved in creating anthocyanins were more active in the purplish-red leaves. Specifically, genes like CHS (chalcone synthase) – crucial for flavonoid biosynthesis – were ‘up-regulated’, meaning their activity was increased. Transcription factors, particularly those belonging to the MYB family, also showed increased activity, further boosting anthocyanin production. This study builds on previous research showing that anthocyanin accumulation is linked to leaf color in other plants, such as chokecherry[3]. That earlier work identified specific genes (PAL, CHI, UFGT, BZ1) involved in anthocyanin production and regulation, and found that variations in their expression correlated with different leaf colors. The current mulberry study reinforces this idea, identifying CHS and MYB genes as key players in the process. Anthocyanins aren’t just about color. They also act as antioxidants, protecting plants from damage[2]. The researchers propose that the increased anthocyanin levels in young, purplish-red leaves may provide protection until the leaves fully develop their ability to absorb light and convert it into energy through photosynthesis. This suggests anthocyanins play a role in balancing energy capture and use in young plant tissues. The researchers used chromatography, a technique mentioned in earlier studies[2], to separate and measure the different anthocyanins present in the leaves. This allowed them to pinpoint delphinidin-3-O-glucoside as the primary driver of the purplish-red color. The study also highlights how environmental factors like pH, light, and temperature can influence anthocyanin color and stability[2]. The findings from Southwest University contribute to a growing understanding of the complex molecular mechanisms behind leaf coloration. This knowledge could be used to breed new plant varieties with enhanced ornamental qualities or to improve the nutritional value of crops by increasing their anthocyanin content.

GeneticsBiochemPlant Science

References

Main Study

1) Molecular and metabolic insights into purplish leaf coloration through the investigation of two mulberry (Morus alba) genotypes.

Published 23rd January, 2024

https://doi.org/10.1186/s12870-024-04737-x

Related Studies

2) Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits.

https://doi.org/10.1080/16546628.2017.1361779

3) Molecular and Metabolic Insights into Anthocyanin Biosynthesis for Leaf Color Change in Chokecherry (Padus virginiana).

https://doi.org/10.3390/ijms221910697


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