Expression patterns of members of the ethylene signaling–related gene families in response to dehydration stresses in cassava

Abstract

Drought is the one of the most important environment stresses that restricts crop yield worldwide. Cassava (Manihot esculenta Crantz) is an important food and energy crop that has many desirable traits such as drought, heat and low nutrients tolerance. However, the mechanisms underlying drought tolerance in cassava are unclear. Ethylene signaling pathway, from the upstream receptors to the downstream transcription factors, plays important roles in environmental stress responses during plant growth and development. In this study, we used bioinformatics approaches to identify and characterize candidate Manihot esculenta ethylene receptor genes and transcription factor genes. Using computational methods, we localized these genes on cassava chromosomes, constructed phylogenetic trees and identified stress-responsive cis-elements within their 5’ upstream regions. Additionally, we measured the trehalose and proline contents in cassava fresh leaves after drought, osmotic, and salt stress treatments, and then it was found that the regulation patterns of contents of proline and trehalose in response to various dehydration stresses were differential, or even the opposite, which shows that plant may take different coping strategies to deal with different stresses, when stresses come. Furthermore, expression profiles of these genes in different organs and tissues under non-stress and abiotic stress were investigated through quantitative real-time PCR (qRT-PCR) analyses in cassava. Expression profiles exhibited clear differences among different tissues under non-stress and various dehydration stress conditions. We found that the leaf and tuberous root tissues had the greatest and least responses, respectively, to drought stress through the ethylene signaling pathway in cassava. Moreover, tuber and root tissues had the greatest and least reponses to osmotic and salt stresses through ethylene signaling in cassava, respectively. These results show that these plant tissues had differential expression levels of genes involved in ethylene signaling in response to the stresses tested. Moreover, after several gene duplication events, the spatiotemporally differential expression pattern of homologous genes in response to abiotic and biotic stresses may imply their functional diversity as a mechanism for adapting to the environment. Our data provide a framework for further research on the molecular mechanisms of cassava resistance to drought stress and provide a foundation for breeding drought-resistant new cultivars.

Involvement of abscisic acid-responsive element-binding factors in cassava (Manihot esculenta) dehydration stress response

“…The ABF family of bZIP transcription factors functions in ABA signaling pathways and plays an important role in plant responses to stresses 18,21 . Here we found that in various cassava organs, MeABFs exhibited differential expression patterns after drought, osmotic, and salt stress treatments(Figs 2–5), which was consistent with trends we observed in cassava in our previous study that identified genes involved in ethylene signaling in response to dehydration stresses 8 . Our results of this study showed that drought stress in cassava leaves and roots, osmotic stress in cassava tuberous roots, and salt stress in cassava stems induced expression of the highest number of MeABFs in terms of significantly elevated expression (Supplementary Tables S5, S8, S11 and S14).…”

“…Since the plants lived for 18 days after drought treatment, we collected materials at 0 d, 3 d, 6 d, 9 d, 12 d, 15 d and 18 d after drought treatment. For osmotic or salt stress treatments, samples were collected at 0, 1, 2, 4, 8, 12, and 24 h after treatment with 400 mM NaCl or 30% PEG-6000 8 . For the control, cassava plants were watered on intervals of every three days.…”

“…To isolate MeABF and MeBADH genes, the nucleotide and amino acid sequences of AtABFs and Arabidopsis thaliana BADHs ( AtBADHs ) were downloaded from the database of TAIR (http://www.arabidopsis.org). The nucleotide and amino acid sequences of MeABF and MeBADH family members were searched using BLAST server and AtABF and AtBADH sequences as the query at Phyzotome (http://phytozome.jgi.doe.gov/pz/portal.html) database and NCBI (http://www.ncbi.nlm.nih.gov/) database 8 .…”

“…However, the mechanisms underlying the stress tolerance of cassava remain unclear. Drought is a major abiotic stress that can reduce crop output 8 . In some areas that experience unpredictable water shortages, enhancement of plant resistance or tolerance to drought is important for minimizing crop losses 8 .…”

“…Drought is a major abiotic stress that can reduce crop output 8 . In some areas that experience unpredictable water shortages, enhancement of plant resistance or tolerance to drought is important for minimizing crop losses 8 . Various strategies to combat drought stress include maintaining water status through rapid stomatal closure and changes in growth and development patterns 9 .…”