Identification of Novel Loci Regulating Interspecific Variation in Root Morphology and Cellular Development in Tomato    

Abstract

While the Arabidopsis (Arabidopsis thaliana) root has been elegantly characterized with respect to specification of cell identity, its development is missing a number of cellular features present in other species. We have characterized the root development of a wild and a domesticated tomato species, Solanum pennellii and Solanum lycopersicum 'M82.' We found extensive differences between these species for root morphology and cellular development including root length, a novel gravity set point angle, differences in cortical cell layer patterning, stem cell niche structure, and radial cell division. Using an introgression line population between these two species, we identified numerous loci that regulate these distinct aspects of development. Specifically we comprehensively identified loci that regulate (1) root length by distinct mechanisms including regulation of cell production within the meristem and the balance between cell division and expansion, (2) the gravity set point angle, and (3) radial cell division or expansion either in specific cell types or generally across multiple cell types. Our findings provide a novel perspective on the regulation of root growth and development between species. These loci have exciting implications with respect to regulation of drought resistance or salinity tolerance and regulation of root development in a family that has undergone domestication.

Hairy Root Transformation Using Agrobacterium rhizogenes as a Tool for Exploring Cell Type-Specific Gene Expression and Function Using Tomato as a Model

“…Recent work has characterized tomato root development in the domesticated and wild species Solanum lycopersicum 'M82' and Solanum pennellii, respectively (Ron et al, 2013). A wide variety of cellular traits were identified that differ between these two species, including differences in cortex radial patterning, changes in cell number in distinct cell types, and differences in cell type differentiation (Ron et al, 2013). Candidate loci that regulate root length, root growth angle, and cell patterning were inferred using genetic approaches enabled by the sequencing of the tomato genome (Ron et al, 2013).…”

“…A wide variety of cellular traits were identified that differ between these two species, including differences in cortex radial patterning, changes in cell number in distinct cell types, and differences in cell type differentiation (Ron et al, 2013). Candidate loci that regulate root length, root growth angle, and cell patterning were inferred using genetic approaches enabled by the sequencing of the tomato genome (Ron et al, 2013). To test the function of these candidate genes, transformation of the appropriate genotype is necessary.…”

Morphological Plant Modeling: Unleashing Geometric and Topological Potential within the Plant Sciences

“…At the cellular level, root cortex cell number (Ron et al, 2013), the cellular basis of carpel size (Frary et al, 2000), and epidermal cell area and number (Tisné et al, 2008) have been analyzed. The genetic basis of cellular morphology ultimately affects organ morphology, and quantitative genetic bases for fruit shape (Paran and van der Knaap, 2007;Monforte et al, 2014), root morphology (Zhu et al, 2005;Clark et al, 2011;Topp et al, 2013;Zurek et al, 2015), shoot apical meristem shape (Leiboff et al, 2015;Thompson et al, 2015), leaf shape (Langlade et al, 2005;Ku et al, 2010;Tian et al, 2011;Chitwood et al, 2014a,b;Zhang et al, 2014;Truong et al, 2015), and tree branching (Kenis and Keulemans, 2007;Segura et al, 2009) have been described.…”

Natural Variation of Root Traits: From Development to Nutrient Uptake

“…In an interspecies cross of a wild tomato (Solanum peruvianum) and a domesticated tomato (Solanum lycopersicum) species, numerous loci for multiple traits could be mapped, some of which cannot be found in the simple Arabidopsis root (Ron et al, 2013). Multiple studies for traits related to RSA were also conducted in rice (Oryza sativa).…”