A Casparian strip domain-like gene, CASPL, negatively alters growth and cold tolerance.

Jinghua Yang,Reena Narsai,Mingfang Zhang,Jim Whelan,Zhongyuan Hu,Changqing Ding,Baochen Xu,Cuiting Chen

doi:10.1038/srep14299

Abstract

A cold-induced transcript encoding a Casparian strip membrane domain (CASP)-like protein (ClCASPL) was identified in watermelon (Citrullus lanatus). Fluorescence microscopy analysis showed that ClCASPL-GFP is localized in the plasma membrane. The orthologous gene in Arabidopsis thaliana (AtCASPL4C1) was also found to play an important role in cold tolerance. Expression analysis using a β-glucuronidase (GUS) reporter reveals that AtCASPL4C1 is widely expressed in a variety of organs and is cold inducible. Analysis of AtCASPL4C1 T-DNA knock-out plants showed altered growth dynamics, faster growth, increased biomass (dry weight) and earlier flowering compared to wild type (Col-0) and ClCASPL overexpressing plants. AtCASPL4C1 knock-out plants showed elevated tolerance to cold stress, while overexpressing CICASPL resulted in increased sensitivity to cold stress in Arabidopsis. Interestingly, AtCASPL4C1 knock-out plants did not display significant alterations in the Casparian strip formation in roots. Thus, the combination of these results suggests a role for CICASPL and AtCASPL4C1 beyond Casparian strip formation in roots, possibly indicating a more fundamental role in vascular tissue.

Highlights

A cold-induced transcript encoding a Casparian strip membrane domain (CASP)-like protein (ClCASPL) was identified in watermelon (Citrullus lanatus)
We investigated the role of ClCASPL and AtCASPL4C1 in growth and cold tolerance in watermelon and Arabidopsis, respectively
The SALK_034800C line was used for screening of homozygous Atcaspl4c1 knock-out mutant plants. 3-week-old plants in Jiffy seedling culture substrate or 2-week-old seedlings cultured in 1/2 MS medium of wild type (WT), Atcaspl4c1 and OX-ClCASPL Arabidopsis were used for analysis of cold stress and phenotypes evaluations

Summary

Introduction

A cold-induced transcript encoding a Casparian strip membrane domain (CASP)-like protein (ClCASPL) was identified in watermelon (Citrullus lanatus). Plants have evolved complex signaling networks to adapt to abiotic stresses via modulating various physiological and biochemical processes[1,2,3] These stress signals are perceived by receptors, transduced and propagated by downstream effectors, altering the expression of a variety of genes that determine growth, tolerance and/or survival depending on the severity of the environmental conditions[2,4]. Recent reports showed that the Casparian strip is composed of a lignin polymer without suberin in Arabidopsis[11] This lignin polymer structure generates a para-cellular barrier, analogous to tight junctions in animals, that is thought to be crucial for selective nutrient uptake, exclusion of pathogens, and many other processes[10]. Evolutionary analysis of CASP family genes indicated that CASPL genes belong to the MARVEL (MAL and related proteins for vesicle trafficking and membrane link) protein family, which has only been experimentally described in metazoans, to date[12]

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