Mutations in the RETICULATA gene dramatically alter internal architecture but have little effect on overall organ shape in Arabidopsis leaves

Abstract

A number of mutants have been described in Arabidopsis, whose leaf vascular network can be clearly distinguished as a green reticulation on a paler lamina. One of these reticulate mutants was named reticulata (re) by Rédei in 1964 and has been used for years as a classical genetic marker for linkage analysis. Seven recessive alleles of the RE gene were studied, at least four of which seem to be null. Contrary to many other leaf mutants studied in Arabidopsis, very little pleiotropy was observed in the external morphology of the re mutants, whose only aberration obvious at first sight is the reticulation exhibited by cotyledons and leaves. The re alleles caused a marked reduction in the density of mesophyll cells in interveinal regions of the leaf, which does not result from perturbed plastid development in specific cells, but rather from a dramatic change in internal leaf architecture. Loss of function of the RE gene seems to specifically perturb mesophyll cell division in the early stages of leaf organogenesis. The leaves of re mutants were nearly normal in shape in spite of their extremely reduced mesophyll cell density, suggesting that the epidermis plays a major role in regulating leaf shape in Arabidopsis. The RE gene was positionally cloned and found to be expressed in all the major organs studied. RE encodes a protein of unknown function and is identical to the LCD1 gene, which was identified based on the increased sensitivity to ozone caused by its mutant allele lcd1-1. Double mutant analyses suggest that RE acts in a developmental pathway that involves CUE1 but does not include DOV1.

Lessons from a search for leaf mutants in Arabidopsis thaliana

“…The re mutant was initially isolated by Rédei and Hirono (1964), and used as a classic phenotypic marker for mapping for many years. Our histological characterization of re mutants shows a significant reduction in mesophyll cell density but little effects on leaf shape, indicating that RE is normally required for the development of internal leaf tissues (González-Bayón et al, 2006). These results were obtained in collaboration with the group of Kevin Pyke and suggest that the epidermis plays a major role in controlling leaf shape in Arabidopsis thaliana, whereas the division and expansion of the internal tissues appear to be secondary in this process, as in tobacco leaves (Avery, 1933).…”

“…Contrary to all genes discussed above, no clear function could be assigned to the RETICULATA (RE) gene (González-Bayón et al, 2006), named LOWER CELL DENSITY1 (LCD1) by Barth and Conklin (2003). The RE gene is ubiquitously expressed, and the RE protein has been identified in the chloroplast proteome (Dunkley et al, 2006).…”

A Journey Through a Leaf: Phenomics Analysis of Leaf Growth inArabidopsis thaliana

“…Leaf thickness is determined by dorso-ventral leaf expansion, which is influenced by both genotype and environment (González-Bayón et al, 2006;Wuyts et al, 2012;Kalve et al, 2014b). To assess overall leaf thickness, histological (Beeckman and Viane, 2000;Kalve et al, 2014b) .…”

“…Analogous to heteroblasty, different rosette leaves within an accession (González-Bayón et al, 2006) and equivalent leaves from various accessions display different venation patterns (Candela et al, 1999). Quantification of leaf venation parameters are facilitated by dark-field images of cleared leaves, in which lignified mature xylem vessels stand out due to their light-scattering properties.…”

The Enzyme-Like Domain of Arabidopsis Nuclear β-Amylases Is Critical for DNA Sequence Recognition and Transcriptional Activation

“…ANAC102 was shown to be a transcription factor involved in stress responses during seed germination (Christianson et al, 2009). In addition, the BZR1-BAM-responsive gene set contains factors involved in cell division including LCD1 (allelic to RETICULATA), which influences cell density in the palisade parenchyma and is important for normal leaf development (Barth and Conklin, 2003;González-Bayón et al, 2006), and the cyclin p3;1 (CYCP3;1). Interestingly, CYCP3;1 belongs to the PHO80-like proteins (Torres Acosta et al, 2004).…”