Abstract
Crop wild relatives harbor exotic and novel genetic resources, which hold great potential for crop improvement. Ipomoea imperati is a wild diploid relative of sweet potato with the capability of high salinity tolerance. We compared the transcriptomes of I. imperati under salt stress vs. control to identify candidate genes and pathways involved in salt response. De novo assembly produced 67,911 transcripts with a high depth of coverage. A total of 39,902 putative genes were assigned annotations, and 936 and 220 genes involved in salt response in roots and leaves, respectively. Functional analysis indicated a whole system response during salt stress in I. imperati, which included four metabolic processes: sensory initiation, transcriptional reprogramming, cellular protein component change, and cellular homeostasis regulation. We identified a number of candidate genes involved in the ABA signaling pathway, as well as transcription factors, transporters, antioxidant enzymes, and enzymes associated with metabolism of synthesis and catalysis. Furthermore, two membrane transporter genes, including vacuole cation/proton exchanger and inositol transporter, were considered to play important roles in salt tolerance. This study provided valuable information not only for understanding the genetic basis of ecological adaptation but also for future application in sweet potato and other crop improvements.
Highlights
Soil salinity is one of the most severe constraints on global crop production
After one day treatment with 600 mM NaCl, we observed a slightly delayed development in the treated plants compared with control plants (Fig. 1); The new 8th leaf was developed in the control plants, while no new leaf emerged in the treated plants
Under high salt treatment (600 mM NaCl), I. imperati mobilizes many genes related to a variety of biological processes as part of a whole cellular responsive system
Summary
Soil salinity is one of the most severe constraints on global crop production. With the combined pressures of climate change and human population growth, salt tolerance is becoming an important agronomic trait to investigate for sustaining or even increasing the world’s food supply in marginal and high saline soils[1]. Hundreds of potential salt-responsive genes have been identified and analyzed to determine their expression patterns under salt treatments These studies reveal molecular mechanisms in response to salt stress, including the salt overly sensitive (SOS) pathway, hormone signaling pathways, ion homeostasis, Reactive oxygen species (ROS) homeostasis, and osmotic regulation[7,8,9]. Salt tolerance is a complex trait that has evolved independently by different mechanisms in diverse lineages[21] Those salt tolerant candidate genes obtained from genetically distant species might not be effective in sweet potato. Sweet potato itself is salt sensitive, while its close wild relative, I. imperati, is a halophytic plant species[22]. Few studies have investigated this species, and information about salt tolerance physiology, morphology, and molecular mechanism in beach morning glory is lacking. The adaptation to saline environments may be more exclusively attributed to the alteration in gene regulation[2, 4, 24], which makes I. imperati extremely attractive for investigating its gene regulation strategies under salt stress
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