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From Roberto Mangani

To my eyes, Laura Cinti’s transgenic cactus looks unnatural (28 February, p 44). The photo shows human hair apparently sprouting from the areolas (the cactus buds). Here is exactly where one would expect to see spines grow from in a normal cactus. But a cactus areola and a mammal hair bulb are two quite specialised and basically different structures. It is impossible to simply turn one into the other.

Moreover, no plant produces keratin, the protein that builds human hair, while no animal produces lignin, the main constituent of cactus spines. So, which of the two substances is the cactus hair made of?

Genetic engineering can only insert single genes into cells, so this cannot be the technique used here. Is this a hybrid obtained in a cell culture? As far as I know, hybrid plant-animal cells never develop into fully grown individuals.

To cut a long story short, the human-cactus is, to me, an obvious fake.

Laura Cinti writes:

• We created the transgenic cactus by germinating cactus seeds in a sterile medium. The tiny plants were cut to create a callus, or wound site. A natural plant pathogen, Agrobacterium tumifaciens, was modified to include keratin genes. This pathogen enters plants through sites of damage, such as a callus, thus inserting the keratin genes into the cactus. The cacti were then grown on, and expressed the keratin gene as fine hairs. Further details of the process are available at my website .

Florence, Italy