MECHANISMS OF TOLERANCE TO SALINITY IN BANANA:PHYSIOLOGICAL, BIOCHEMICAL,AND MOLECULAR ASPECTS

Lilia Willadino,Marta Barbosa Ribeiro,Daniel Oliveira Jordão Do Amaral,Flavia Suassuna,Terezinha Rangel Camara,Márcia Vanusa Da Silva

doi:10.1590/0100-29452017723

Abstract

ABSTRACT In the northeastern region of Brazil, saline soils are constraints to banana production, becoming necessary to understand the mechanisms of salt tolerance. Two bananas genotypes, Tap Maeo, tolerant, and Berlin, sensitive, were subjected to treatment with 50 mol m-3 NaCl or without salt. This study evaluated the effects of salt on the following physiological aspects: leaf area, content and distribution of Na+, membrane integrity, proton AT Pase activity. Besides, a search for differentially expressed genes was performed using the Differential Display technique. Tap Maeo genotype showed the smallest reduction in leaf area, smaller accumulation of Na+ and malondialdehyde (MDA), and higher activity of proton AT Pase activity. Two sequences differentially expressed in the tolerant genotype, (Musa 07, Musa 23), shared a high degree of identity with the amino acid sequences of the genes SOS1 and SOS2, respectively. The clone Musa 10 was highly similar to amino acid sequence of the ascorbate peroxidase gene, and Musa 26, encodes the enzyme betaine aldehyde dehydrogenase. These significant biological markers indicate that salinity tolerance in banana involves at least two simultaneous mechanisms: the activation of the SOS pathway, increasing the extrusion of Na+, and the activation of antioxidative system, increasing the synthesis of APX and betaine aldehyde dehydrogenase enzyme.

Highlights

Salinity is one of the most significant abiotic stresses in the world, constituting a limiting factor that adversely affects the growth of plants in general and the productivity of agricultural crops
The leaf area reduction that occurs due to the increase of the levels of salt is a common response in banana and has been previously described in 46 genotypes evaluated by different researchers (GOMES et al, 2004; SILVA et al, 2009; FERRAZ, 2008; WILLADINO et al, 2011); these genotypes exhibited reductions in leaf area that varied from 16.3 to 69.2%
Decreased leaf area is related to constrained CO2 fixation, which reduces the net assimilation rate and increases the production of reactive oxygen species (ROS) through the Mehler reaction (MILLER et al, 2009)

Summary

Introduction

Salinity is one of the most significant abiotic stresses in the world, constituting a limiting factor that adversely affects the growth of plants in general and the productivity of agricultural crops. The salt SOS pathway functionally consists of the Na+ transporter, SOS1, the protein kinase SOS2, and the Ca2+ sensor SOS3, which constitute a functional model that ensures ionic homeostasis in plants that are adapted or tolerant to saline stress (FEKI et al, 2014). Another important mechanism for tolerance is the increase in the activity of antioxidant enzymes, to avoid the effects of oxidative stress (FOYER; SHIGEOKA 2011). This is a mechanism that avoid the accumulation of reactive oxygen species (ROS) that causes damage to nucleic acids, proteins, membrane lipid peroxidation and disrupt the redox homeostasis (AZOOZ et al, 2009)

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Results