The Salt Sensitivity Induced by Disruption of Cell Wall-Associated Kinase 1 (SlWAK1) Tomato Gene Is Linked to Altered Osmotic and Metabolic Homeostasis

Victoriano Meco,Fredy Barneche,Isabel Egea,Elisabeth Esch,Ana Ortíz-Atienza,Stéphanie Drevensek,Francisco B Flores,María C Bolarin,Fernando J Yuste-Lisbona,Rafael Lozano,Wim Vriezen

doi:10.3390/ijms21176308

Abstract

Tomato cell wall-associated kinase 1 (SlWAK1) has only been studied in biotic stress response and hence its function in abiotic stress remains unknown. In a screening under salinity of an insertional mutant collection of tomato (Solanum lycopersicum L.), a mutant exhibiting lower degree of leaf chlorosis than wild type (WT) together with reduced leaf Na+ accumulation was selected. Genetic analysis of the mutation revealed that a single T-DNA insertion in the SlWAK1 gene was responsible of the mutant phenotype. Slwak1 null mutant reduced its shoot growth compared with WT, despite its improved Na+ homeostasis. SlWAK1 disruption affected osmotic homeostasis, as leaf water content was lower in mutant than in WT under salt stress. In addition, Slwak1 altered the source-sink balance under salinity, by increasing sucrose content in roots. Finally, a significant fruit yield reduction was found in Slwak1 vs. WT under long-term salt stress, mainly due to lower fruit weight. Our results show that disruption of SlWAK1 induces a higher sucrose transport from source leaf to sink root, negatively affecting fruit, the main sink at adult stage.

Highlights

Salt stress is responsible for reduced crop growth and the cause of important economic losses in agricultural production
In the salt-tolerant wild tomato species Solanum pennellii we observed that endogenous Na+ concentration increased rapidly after applying salt stress in order to maintain the osmotic homeostasis and avoid the yield penalties [5], while the high ion exclusion in tomato induced by higher use of organic solutes to re-establish osmotic homeostasis occurs at the cost of plant growth [6]
During the screening for salinity tolerance of segregating populations (T2) coming from a T-DNA collection generated in tomato (S. lycopersicum L. cv Moneymaker), a mutant line was selected for its lower degree of leaf chlorosis compared with wild type (WT) plants, suggesting that this might be a salt

Summary

Introduction

Salt stress is responsible for reduced crop growth and the cause of important economic losses in agricultural production. In the salt-tolerant wild tomato species Solanum pennellii we observed that endogenous Na+ concentration increased rapidly after applying salt stress in order to maintain the osmotic homeostasis and avoid the yield penalties [5], while the high ion exclusion in tomato induced by higher use of organic solutes to re-establish osmotic homeostasis occurs at the cost of plant growth [6]. Tomato tolerance to salt stress is not the result of only one mechanism; the osmotic homeostasis may be the predominant mechanism to avoid a high energetic cost, but in other circumstances it may be ion homeostasis to avoid Na+ toxicity the predominant mechanism

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Conclusion