TheTORNADO1andTORNADO2Genes Function in Several Patterning Processes during Early Leaf Development inArabidopsis thaliana

Abstract

In multicellular organisms, patterning is a process that generates axes in the primary body plan, creates domains upon organ formation, and finally leads to differentiation into tissues and cell types. We identified the Arabidopsis thaliana TORNADO1 (TRN1) and TRN2 genes and their role in leaf patterning processes such as lamina venation, symmetry, and lateral growth. In trn mutants, the leaf venation network had a severely reduced complexity: incomplete loops, no tertiary or quaternary veins, and vascular islands. The leaf laminas were asymmetric and narrow because of a severely reduced cell number. We postulate that the imbalance between cell proliferation and cell differentiation and the altered auxin distribution in both trn mutants cause asymmetric leaf growth and aberrant venation patterning. TRN1 and TRN2 were epistatic to ASYMMETRIC LEAVES1 with respect to leaf asymmetry, consistent with their expression in the shoot apical meristem and leaf primordia. TRN1 codes for a large plant-specific protein with conserved domains also found in a variety of signaling proteins, whereas TRN2 encodes a transmembrane protein of the tetraspanin family whose phylogenetic tree is presented. Double mutant analysis showed that TRN1 and TRN2 act in the same pathway.

Expression of DOF genes identifies early stages of vascular development in Arabidopsis leaves

“…Available evidence, however, suggests that the selection process terminates with emergence of files of ground cells that have activated expression of the HD-ZIP III gene ATHB8 and that will successively elongate into procambial cells (AlonsoPeral et al, 2006;Candela et al, 2001;Carland and Nelson, 2004;Cnops et al, 2006;Donner et al, 2009;Kang and Dengler, 2004;Koizumi et al, 2000;Petricka and Nelson, 2007;Sawchuk et al, 2007Sawchuk et al, , 2008Scarpella et al, 2004Scarpella et al, , 2006. Therefore, the events preceding acquisition of the ATHB8 preprocambial cell state are crucial for vein formation.…”

“…Initiation of ATHB8 expression is directly controlled by MP (Donner et al, 2009), and identifies acquisition of a critical and typically irreversible 'preprocambial' cell state that accurately predicts sites of vascular differentiation (Alonso-Peral et al, 2006;Candela et al, 2001;Carland and Nelson, 2004;Cnops et al, 2006;Donner et al, 2009;Kang and Dengler, 2004;Koizumi et al, 2000;Petricka and Nelson, 2007;Pineau et al, 2005;Sawchuk et al, 2007Sawchuk et al, , 2008Scarpella et al, 2004Scarpella et al, , 2006. A view of the transcriptional landscape of cells at preprocambial stages would be particularly valuable as it might provide insight into the molecular pathways underlying vein formation.…”

The VASCULATURE COMPLEXITY AND CONNECTIVITY Gene Encodes a Plant-Specific Protein Required for Embryo Provasculature Development

“…However, this extracellular loop is not a defining feature of TET function, since it is absent in a subgroup of human TETs called the fourtransmembrane L6 superfamily (Wright et al, 2000). Of the 17 TET genes in Arabidopsis (Wang et al, 2012), one, TET1/TORNADO2/EKEKO, has been shown to be required for leaf and root patterning (Olmos et al, 2003;Cnops et al, 2006). In addition, like vcc and ops mutant lines, mutants in TET1/TORNADO2/EKEKO also show defects in cotyledon vein patterning (Cnops et al, 2006).…”

“…Of the 17 TET genes in Arabidopsis (Wang et al, 2012), one, TET1/TORNADO2/EKEKO, has been shown to be required for leaf and root patterning (Olmos et al, 2003;Cnops et al, 2006). In addition, like vcc and ops mutant lines, mutants in TET1/TORNADO2/EKEKO also show defects in cotyledon vein patterning (Cnops et al, 2006). Some plant TETs localize to the plasma Figure 8.…”

Simultaneous activation of SHR and ATHB8 expression defines switch to preprocambial cell state in Arabidopsis leaf development

“…Onset of ATHB8 expression is directly controlled by MP (Donner et al, 2009), and identifies transition to a typically irreversible ''preprocambial'' cell state that accurately predicts sites of leaf vein formation (e.g., Koizumi et al, 2000;Carland and Nelson, 2004;Kang and Dengler, 2004;Scarpella et al, 2004Scarpella et al, , 2006Pineau et al, 2005;Alonso-Peral et al, 2006;Cnops et al, 2006;Petricka and Nelson, 2007;Sawchuk et al, 2007Sawchuk et al, , 2008Donner et al, 2009;Carland et al, 2010). Therefore, characterization of the transcriptional profile of ground cells that have switched to preprocambial state would be particularly desirable as it may provide insight into the molecular pathways controlling vein formation.…”