Gene Expression Patterns in Roots of Camelina sativa With Enhanced Salinity Tolerance Arising From Inoculation of Soil With Plant Growth Promoting Bacteria Producing 1-Aminocyclopropane-1-Carboxylate Deaminase or Expression the Corresponding acdS Gene.

Zohreh Heydarian,Dwayne D Hegedus,Margaret Gruber,Bernard R Glick

doi:10.3389/fmicb.2018.01297

Abstract

Camelina sativa treated with plant growth-promoting bacteria (PGPB) producing 1-aminocyclopropane-1-carboxylate deaminase (acdS) or transgenic lines expressing acdS exhibit increased salinity tolerance. AcdS reduces the level of stress ethylene to below the point where it is inhibitory to plant growth. The study determined that several mechanisms appear to be responsible for the increased salinity tolerance and that the effect of acdS on gene expression patterns in C. sativa roots during salt stress is a function of how it is delivered. Growth in soil treated with the PGPB (Pseudomonas migulae 8R6) mostly affected ethylene- and abscisic acid-dependent signaling in a positive way, while expression of acdS in transgenic lines under the control of the broadly active CaMV 35S promoter or the root-specific rolD promoter affected auxin, jasmonic acid and brassinosteroid signaling and/biosynthesis. The expression of genes involved in minor carbohydrate metabolism were also up-regulated, mainly in roots of lines expressing acdS. Expression of acdS also affected the expression of genes involved in modulating the level of reactive oxygen species (ROS) to prevent cellular damage, while permitting ROS-dependent signal transduction. Though the root is not a photosynthetic tissue, acdS had a positive effect on the expression of genes involved in photosynthesis.

Highlights

The ability of Camelina sativa to grow on marginal lands which are not well-suited for food crops has piqued interest in its development as an industrial oilseed crop for biofuels, bio-lubricants, and animal feed (Blackshaw et al, 2011; Li and Mupondwa, 2014)
This study examined how gene expression patterns in roots responding to salt stress were affected by the expression of aminocyclopropane1-carboxylate deaminase (acdS) under the control of broadly constitutive (CaMV 35S) or rootspecific promoters in transgenic lines, or by growth in soils treated with plant growth-promoting bacteria (PGPB) producing acdS
Jasmonic acid-mediated adaptation to salinity stress occurs in barley and sweet potato (Walia et al, 2007; Zhang et al, 2017); none of the genes involved in JA biosynthesis or signaling were differentially expressed during salt treatment in roots of the 35S::acdS line or in plants treated with P. migulae 8R6

Summary

Introduction

The ability of Camelina sativa (camelina) to grow on marginal lands which are not well-suited for food crops has piqued interest in its development as an industrial oilseed crop for biofuels, bio-lubricants, and animal feed (Blackshaw et al, 2011; Li and Mupondwa, 2014). Undifferentiated polyploidy and little fractionation bias in the C. sativa genome presents significant challenges for breeding and genetic manipulation (Kagale et al, 2014; Kanth et al, 2015; Poudel et al, 2015). This situation necessitates exploration of alternate strategies for trait improvement in camelina. One such approach for improving salt tolerance is the application of plant growth-promoting bacteria (PGPB) that are found in association with plant roots (rhizospheric) or within plant tissues (endophytic) (Bacon and Hinton, 2006; Ali et al, 2012), and facilitate plant growth under unfavorable conditions (Glick, 2015). Transgenic lines expressing acdS or plants treated with PGPB producing acdS exhibit increased salinity tolerance (Heydarian et al, 2016)

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