Abstract
Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions.
Highlights
Natural variation is the main source for evolutionary change and the substrate for selection and adaptation of populations to a specific environment (Alonso-Blanco et al, 2009; Hancock et al, 2011; Agren and Schemske, 2012; Richards et al, 2012)
Several reports have been focused on analyzing Arabidopsis root natural variation in response to different growth conditions (Ristova and Busch, 2014); little is known about the variation of the root apical meristem (RAM) and the stem cell niche morphology. To analyze such natural variation in Arabidopsis, we studied 12 different accessions that originally were obtained from contrasting habitats and we compared their root system architecture, their root growing dynamics and the RAM size, as well as the stem cell niche morphology
To eliminate variation in size, position and orientation of each accession, and thereby obtain the coordinates superimposed landmarks, that are the core of geometric morphometric for multivariate analysis (Klingenberg, 2011), we performed the least-squares procrustes superimpositions (Dryden and Mardia, 1998) to fitting a model that completely describes the differences between Arabidopsis root shapes of each accession to fit a very simple model that only takes into consideration global parameters such as differences in rotation, translation and scale
Summary
Natural variation is the main source for evolutionary change and the substrate for selection and adaptation of populations to a specific environment (Alonso-Blanco et al, 2009; Hancock et al, 2011; Agren and Schemske, 2012; Richards et al, 2012). Arabidopsis thaliana (Arabidopsis here after) populations that have been collected from particular geographic locations are commonly referred to accessions; these varieties show an ample range of variation in their phenotypical traits (Assmann, 2013; Aliniaeifard and van Meeteren, 2014; Ristova and Busch, 2014) They comprise a key resource to understand the molecular basis of variation, the role of plasticity in adaptive evolution, as well. The function of FRIGIDA and FLOWERING LOCUS C, two proteins involved in the networks underlying flowering time in Arabidopsis was elucidated based on their variation in different accessions (Koornneef et al, 1994; Johanson et al, 2000) While most of such studies have concerned aerial phenotypic variation, root natural variation has been described in fewer cases (Beemster et al, 2002; Mouchel et al, 2004; Ristova and Busch, 2014). We still do not understand the molecular genetics and developmental basis of relevant root traits, their plasticity and role, in conjunction with such environmental factors, during adaptive evolution
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