Abstract
Lateral root development is a complex process regulated by numerous factors. An important role for sugar in lateral root development has been known for a while, but the underlying molecular basis still remains unclear. In this study, we first showed that WOX7, a sugar-inducible negative regulator of lateral root development, acts downstream of the glucose sensor HXK1. Using a transgenic line homozygous for a transgene expressing GFP under the control of the WOX7 promoter, we next performed a genetic screen to identify additional genes in this development pathway. A number of mutants with altered level of WOX7 expression were recovered, and two with increased WOX7 expression, named ewe-1 and ewe-2 (for Enhanced WOX7 Expression), were further characterized. Both mutants manifest delayed lateral root development, and genetic analysis indicates that single recessive mutations are responsible for the observed phenotypes. The mutations were then located to similar regions on chromosome 2 by marker-assisted analyses, and candidate genes were identified through whole genome sequencing. The significance and limitations of this work are discussed.
Highlights
Root is essential to plant growth and development, because it is responsible for water and nutrient uptake from the soil
In a previous study we showed that WOX7, a WUSHEL-related transcription factor, negatively regulates lateral root development in a sugar-dependent manner [25]
We found that the two mutants displayed opposite phenotypes in terms of lateral root number and density, both had an elevated level of WOX7
Summary
Root is essential to plant growth and development, because it is responsible for water and nutrient uptake from the soil. The root expands its surface by generating lateral roots as well as by extending its length. Lateral roots are derived from a subset of cells in the stele through a complex developmental process that is controlled by both internal and environmental factors, including almost all hormones [1,2,3,4], nutrient and water availability [5,6,7,8]. Sugar plays a role in lateral root development and root growth, as both an energy source and signaling molecule [9]. Synthesized in the shoot, sugar is transported to the root as well as other non-photosynthetic organs, mainly in the form of sucrose, which is converted to glucose that can be directly utilized in energy metabolism [10]. At lower concentrations (below 1%), sugar promotes root growth and lateral root formation, but becomes inhibitory at higher concentrations [12,13,14]
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