Biological complexity: life's required specific metals (Introduction)

by David Turell , Tuesday, June 07, 2022, 21:55 (900 days ago) @ David Turell

Copper required to pop open seed pods:

https://phys.org/news/2022-06-copper-seed-pod

"Their findings show that a key micronutrient—copper—is essential for laying down a precise pattern of lignin in the seed pods. Lignin is an abundant plant polymer found in lignocellulose, the main structural material in plants. It is present in plant cells walls and is responsible for making wood stiff.

***

"As Hay explains, "the mechanical design that allows these pods to explode depends on lignin being laid down in a precise pattern in this single layer of cells. We know little about what controls this pattern of lignin deposition, and so we set out to identify the genes that control this process. We found three genes that are required to lignify the cell wall in exploding seed pods. These genes code for enzymes, called laccases, that polymerize lignin. When C. hirsuta plants lack all three laccase genes, they also lack lignin in this specific cell type."

"The research team also discovered another gene, called SPL7, required for C. hirsuta seed pod lignification. This gene encodes a protein that regulates copper levels in plants. The researchers discovered SPL7 in a mutant screen. Mutant plants that lack this gene, also lack lignin in endocarpb cell walls. Without lignin, they could no longer disperse their seeds widely. These effects were reversed when the SPL7 mutant plants were grown in soil with high copper levels, but not when they were grown in soil with low copper levels. SPL7 therefore helps C. hirsuta plants to acquire enough copper to develop fully exploding seed pods, especially when copper levels are low.

"But how does copper affect the mechanical structure of these exploding seed pods?

"Interestingly, laccases are copper binding proteins that depend on copper for their function. "The link between these two findings is copper," says Hay. "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 the mechanics of exploding seed pods, and copper-requiring laccases regulate this lignification, this makes seed dispersal dependent on the control of copper levels by SPL7."

"These findings provide important new insights into the genes and cellular processes that generate these extraordinary exploding structures. 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.

"Copper deficiency in soil affects plants and trees in many different ways and is tackled by using copper fertilizers. It is a particular problem for forestry, as low copper levels can cause tree weakening as a result of poor lignification. "Our work makes a molecular link between copper and lignin via SPL7 and laccases. These insights could inspire new approaches for sustainable forest management," Hay explains."

Comment: how does a blind evolutionary process reach out to choose copper specifically for the active proteins. Not hunt and peck but a designer wouild have no problem