All for one and one for all

 作者:尹弄     |      日期:2019-03-08 02:03:26
By Bob Holmes A SINGLE gene may guide individuals within colonies of tiny animals called hydroids to develop in radically different ways, say researchers. Hydroids, which are relatives of hydra, take the form of polyps, and have a base at one end and tentacles at the other. Individual hydroids in some species are highly specialised. Some members of a colony do all the eating, others reproduce and some are little more than a single stinging tentacle. Paulyn Cartwright and her colleagues at Yale University monitored the activity of a gene called Cnox-2 that defines the head-to-tail axis of the body as polyps develop. They found that feeding polyps have lots of the gene’s protein product near their base, but little up near the tentacles. Defensive polyps, which have pronounced tentacles, have little Cnox-2 anywhere (Proceedings of the National Academy of Sciences, vol 96, p 2183). When Cartwright removed all the feeding polyps from a colony, she found that some defensive polyps changed into the feeding form. In the transformed polyps, Cnox-2 became more abundant near their base. The study is the first to show that a single gene can dictate much of the specialisation in colonial animals,