کشف نقش Small RNAs در شکل گیری برگ
Mobile Small RNAs Set Up Leaf Patterning In Plants
ScienceDaily (Feb. 28, 2009) — A key item in the developmental agenda of a plant leaf is the establishment of an axis that makes a leaf's top half distinct from its bottom half. This asymmetry is crucial for the leaf's function: it ensures that the leaf develops a flattened blade that is optimized for photosynthesis, with a top surface specialized for light harvesting and a bottom surface containing tiny pores that serve as locales for gas exchange.
For years, plant biologists have known that this top/bottom axis – analogous to the front/back or "dorso-ventral" axis in animals – is established by a signal derived from the meristem, the stem cell-rich growing tip of the plant from which new leaves arise. Other signals that traffic between the upper and lower sides of the leaf are thought to stably maintain this polar axis. Just as a GPS signal tells drivers where they are, these signals give cells positional information about where they are located within the leaf, causing them to acquire their correct identities by switching specific genes "on" or "off."
Associate Professor Marja Timmermans, Ph.D., and her team of scientists at Cold Spring Harbor Laboratory (CSHL) are the first group to uncover the identity of one such positional signal. In a study that appears in the March 1st issue of Genes and Development, they describe a family of mobile small RNAs that .....................................
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