Studies of plant and animal development were revolutionized by the recent development of green and blue fluorescent markers that let researchers actually watch the movements of important features within living cells. Now UC Davis scientists have devised another fluorescent marker -- a glowing yellow-orange hue that can be used in tandem with the blues and greens. UC Davis biochemist J. Clark Lagarias built the new marker with student John Murphy (now a postdoctoral fellow at UC Berkeley) from a plant light receptor and a pigment from red algae. Lagarias says the yellow-orange label overcomes some shortcomings of the blue and green markers: Its light is brighter and its color is less likely to be confused with a cell's inherent fluorescence, which make it visible at greater depths within living tissue. And this new marker, dubbed "phytofluor," may be used along with the blue and green tags, making it possible to study the actions -- and interactions -- of two different tagged molecules at the same time. Lagarias suggests that phytofluors could be used to track the effects of new drugs, or tagged onto proteins to study normal cellular function and disease. A report on the work appears in this month's issue of the journal Current Biology. Visuals: Color photographs of plant seedlings with structures tagged with bright orange and green colors are available.