Copper makes seed pods explode

What is it about?

The sudden explosion of popping cress (Cardamine hirsuta) relies on a precise pattern of lignin in the seed pods. We found three genes that control this lignin pattern. These genes code for enzymes, called laccases, that polymerize lignin. We conducted a mutant screen to discover other genes involved and identified SPL7 – a transcriptional regulator of copper homeostasis. The link between these two findings is copper. Plants need SPL7 to cope when there’s too little copper in the soil, and laccases need to bind copper for their enzymatic activity. Since lignin is critical for seed pods to explode, and laccases are needed to form lignin, this makes seed dispersal dependent on the control of copper levels by SPL7.

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Photo by Susan Wilkinson on Unsplash

Photo by Susan Wilkinson on Unsplash

Why is it important?

These findings provide important new insights into the genes and cellular processes that generate exploding seed pods. They also shed new light on the role of copper in this process and on the process of lignification itself, which remains little understood. One reason for this is that large families of genes are involved in lignin polymerization in plant cell walls. Working out how each gene is involved is therefore a challenge, but one that could be addressed using approaches reported in this study, such as CRISPR/Cas9 gene editing and conditional gene expression.