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Limiting layer diffusion

SHR (green) starts leaking past its usual endodermal endpoint when SCR isn't there to catch it. BENFEY/AAAS

Adiffusible plant transcription factor is kept from wandering too far by hitching to a nuclear partner, report Hongchang Cui, Philip Benfey (Duke University, Durham, NC), and colleagues.

The wanderer is SHORTROOT (SHR), which is made in the root vascular tissue and then diffuses outward. In the neighboring cell layer, it partners with another transcription factor, called SCARECROW (SCR), to help create the plant endodermal layer. The Arabidopsis endodermis is a single layer surrounding the root vasculature. Benfey and colleagues wondered why SHR's diffusion stops here.

Two cell lines with reduced SCR activity provided the answer. The lower the SCR activity, the more SHR leaked past the first cell layer and began to specify extra endodermis. The effects suggest that SCR physically tethers its partner in the nucleus of the cells where the job must be done. SHR and SCR orthologues also interact in rice and are expressed in similar patterns, suggesting the strategy may be common among plants.

The endodermis's job is to absorb nutrients into the vasculature. Benfey speculates that the diffusive stop helps to ensure that nutrients only have to pass through a single endodermal layer along their way. It may seem baroque, he says, but no more so than diffusion gradients in animals.

Reference:

Cui, H., et al. 2007. Science. 316:421–425.[Abstract/Free Full Text]

Alla Katsnelson

akatsnelson{at}gmail.com

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This Article Full Text (PDF, 1003K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Katsnelson, A. Search for Related Content PubMed Articles by Katsnelson, A. Social Bookmarking                            What's this?