( that each of the seven hormones activat...)Computational analysis shows that plant hormones often go it alone

The microarray data used by Chory's team were collected as part of a multinational effort known as the AtGenExpress project cataloguing gene expression in the model plant Arabidopsis thaliana, which has become the lab mouse of the plant world. The laboratory of Detlef Weigel, Ph.D., an adjunct professor in the Laboratory for Plant Biology at the Salk and a professor at the Max Plank Institute for Developmental Biology in Tübingen, Germany, is one of the most prolific providers of micro-array data for Arabidopsis.

Participants in the project send results from their lab's microarray analysis of Arabidopsis genes to a publicly available database, where data is shared by colleagues investigating diverse biological questions. "The data was there but nobody had compared the effects of different growth hormones on gene expression side by side," says Nemhauser.

The amount of data analyzed by the Chory group was enormous. The activity of about 22,000 genes, each detected by on average 15 detectors after treatment with the seven hormones, was crunched--not once--but twice, resulting in roughly 14 million data points. "Since we didn't generate any of the data ourselves, we had to perform extensive quality controls to extract meaningful information," explains Hong.

The Salk researchers' analysis revealed that surprisingly few genes were switched on by multiple hormones. And when more than one hormone did initiate a similar program, such as activating genes encoding proteins called "expansins" that loosen plant cell walls to allow for growth, the investigators found that they mobilized different members of the expansin gene family.

"The data analysis showed that there is likely a complex set of interactions between the levels of hormones," explains Chory, "which suggests that long-term effect
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Source:Salk Institute