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Abstract
The final size of an organism, or of single organs within an organism, depends on an intricate coordination of cell proliferation and cell expansion. Although organism size is of fundamental importance, the molecular and genetic mechanisms that control it remain far from understood. Here we identify a transcription factor, KUODA1 (KUA1), which specifically controls cell expansion during leaf development in Arabidopsis thaliana. We show that KUA1 expression is circadian regulated and depends on an intact clock. Furthermore, KUA1 directly represses the expression of a set of genes encoding for peroxidases that control reactive oxygen species (ROS) homeostasis in the apoplast. Disruption of KUA1 results in increased peroxidase activity and smaller leaf cells. Chemical or genetic interference with the ROS balance or peroxidase activity affects cell size in a manner consistent with the identified KUA1 function. Thus, KUA1 modulates leaf cell expansion and final organ size by controlling ROS homeostasis.
Highlights
The final size of an organism, or of single organs within an organism, depends on an intricate coordination of cell proliferation and cell expansion
To identify gene networks controlling organ size in Arabidopsis, we performed a reverse genetics screen for genes encoding transcription factors (TFs) that are induced during leaf expansion based on transcriptome data[3]
Complementation of the mutant with the gene’s complementary DNA under control of the CaMV 35S promoter verified that the observed phenotype was caused by the loss of the TF
Summary
The final size of an organism, or of single organs within an organism, depends on an intricate coordination of cell proliferation and cell expansion. Chemical or genetic interference with the ROS balance or peroxidase activity affects cell size in a manner consistent with the identified KUA1 function. KUA1 modulates leaf cell expansion and final organ size by controlling ROS homeostasis. Cell expansion is affected by alterations in cell wall content and architecture[5,6,7] Such alterations may be mediated by biosynthetic and/or remodelling proteins, including expansins, a class of proteins located in plant cell walls[8,9], xyloglucan endotransglucosylase/hydrolases (XETs/ XTHs)[10], and by peroxidases (Prxs), which modulate the level of reactive oxygen species (ROS)[11]. Upb[1] mutants displayed a significantly increased meristem cell number and length of the first cortical cell This indicates that H2O2 scavenging by root peroxidases controls indeterminate root growth[18]. KUA1 directly controls ROS-mediated cell expansion during leaf development to set the final size of the organ
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