The Arabidopsis TETRATRICOPEPTIDE THIOREDOXIN-LIKE Gene Family Is Required for Osmotic Stress Tolerance and Male Sporogenesis

Naoufal Lakhssassi,Verónica G Doblas,Victoriano Valpuesta,Alicia Esteban Del Valle,Antonio J Jimenez,Miguel A Botella,David Posé,Araceli G Castillo,Abel Rosado,Omar Borsani

doi:10.1104/pp.111.188920

Naoufal Lakhssassi, Verónica G Doblas + Show 8 more

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https://doi.org/10.1104/pp.111.188920

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Journal: Plant Physiology	Publication Date: Jan 9, 2012
Citations: 51	License type: CC BY 4.0

Affiliation: Universidad de Málaga

Abstract

TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are characterized by the presence of six tetratricopeptide repeats in conserved positions and a carboxyl-terminal region known as the thioredoxin-like domain with homology to thioredoxins. In Arabidopsis (Arabidopsis thaliana), the TTL gene family is composed by four members, and the founder member, TTL1, is required for osmotic stress tolerance. Analysis of sequenced genomes indicates that TTL genes are specific to land plants. In this study, we report the expression profiles of Arabidopsis TTL genes using data mining and promoter-reporter β-glucuronidase fusions. Our results show that TTL1, TTL3, and TTL4 display ubiquitous expression in normal growing conditions but differential expression patterns in response to osmotic and NaCl stresses. TTL2 shows a very different expression pattern, being specific to pollen grains. Consistent with the expression data, ttl1, ttl3, and ttl4 mutants show reduced root growth under osmotic stress, and the analysis of double and triple mutants indicates that TTL1, TTL3, and TTL4 have partially overlapping yet specific functions in abiotic stress tolerance while TTL2 is involved in male gametophytic transmission.

Highlights

TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are characterized by the presence of six tetratricopeptide repeats in conserved positions and a carboxyl-terminal region known as the thioredoxin-like domain with homology to thioredoxins
The TTLs constitute a family of plant-specific proteins with a common modular architecture containing six tetratricopeptide repeat (TPR) domains distributed in specific positions throughout the sequence and a C-terminal sequence displaying homology to thioredoxins termed the thioredoxin-like (TRXL) motif (Rosado et al, 2006b)
We identified TTL-like proteins containing the TRXL motif and seven to eight TPR motifs that could possibly function as TTL proteins but were not considered in our analysis

Summary

Introduction

TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are characterized by the presence of six tetratricopeptide repeats in conserved positions and a carboxyl-terminal region known as the thioredoxin-like domain with homology to thioredoxins. Little is known about the mechanism(s) coordinating osmosensing and plant cell cycle regulation as well as the adaptive processes required to maintain meristem function under osmotic stress conditions. Overlapping and Specific Functions of the TTL Gene Family in the Arabidopsis TETRATRICOPEPTIDE THIOREDOXIN-LIKE1 gene (TTL1) cause reduced tolerance to NaCl and osmotic stress that is characterized by reduced root elongation, disorganization of the root meristem, and impaired osmotic responses during germination and seedling development (Rosado et al, 2006b). TTL1 is the first characterized member of a novel protein family defined by the presence of six tetratricopeptide repeat (TPR) motifs and a region in the C terminus with homology to class h thioredoxins but lacking essential Cys residues required for thioredoxin activity (Rosado et al, 2006b; Ceserani et al, 2009). TPR domains have been described as proteinprotein interaction modules defined by a pattern of small and large amino acids forming an all-helical secondary structure (Blatch and Lassle, 1999; D’Andrea and Regan, 2003; Yang et al, 2005)

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