The Yin and Yang in leaf polarity – University of Copenhagen

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12 November 2015

The Yin and Yang in leaf polarity

A new paper from Copenhagen Plant Science Centre researchers investigates the role of the transcription factor KANADI1 in repression of genes involved in plant growth.

Development of leaf polarity

Leafs have two sides, the upper (adaxial) and lower (abaxial). The cells of the upper side specialize in photosynthesis, while the lower side takes on an assisting role and enables quick carbon dioxide and oxygen diffusion. How each cell determines its relative orientation is a main challenge in understanding leaf development. The orientation is regulated by the opposing gradients of two transcription factor classes: HD-ZIPIII decides the upper side and KANADI—its antagonist—determines the lower side, by being more abundant there.

Leaf cross-section with the adaxial (upper) and abaxial (lower) domains. Attribution: H McKenna via Wikimedia Commons.

KANADI1 is a negative regulator

A team of international scientists investigate the transcription factor KANADI1 in the Plant Physiology paper "Meta-Analysis of Arabidopsis KANADI1 Direct Target Genes Identifies a Basic Growth-Promoting Module Acting Upstream of Hormonal Signaling Pathways" co-authored by the CPSC members Daniel Straub, Tenai Eguen, and Stephan Wenkel. By comparing their own expression profiling datasets with ones available in the literature, they determine genes regulated by KANADI1. They confirmed that KANADI1 is involved in repressing genes involved in plant growth hormone (auxin) biosynthesis, transport, and signaling.

Shade as a genetic stimulus

The researchers confirmed this negative regulation by performing a series of shading experiments. In their native environment, plants optimize their structure to account for the shade from other organisms or even from themselves. The elongation of their stem allows the plants to further grow in the direction of light. This adaptation depends on auxin and therefore is suppressed by KANADI1, as this article illustrates.

The authors demonstrate that KANADI1 regulates a large amount of genes. Outgoing from these findings, they hypothesize that the KANADI1/HD-ZIPIII pair acts as a more general growth regulator of leafs.

Read more about Associate Professor Wenkel's research on transcription factors and micro-Proteins here.


Written by Anna Holzwarth, PhD student at CPSC

Edited by Konstantinos Vavitsas, PhD fellow in CPSC & Lene Rasmussen, CPSC coordinator.