Abstract
Sesame (Sesamum indicum L.) is one of the most important oilseed crops. It is mainly grown in arid and semi-arid regions with occurrence of unpredictable drought which is one of the major constraints of its production. However, the lack of gene resources associated with drought tolerance hinders sesame genetic improvement towards this osmotic stress. The present research aimed at identifying candidate genes associated with drought tolerance in the whole genome of sesame through homology search of known drought associated genes from three relative species, viz., potato, tomato and the well-described model plant Arabidopsis. Based on 2,495 sequences including 1,150 from Arabidopsis, 1,075 from potato and 270 from tomato, comparative analysis against sesame genome led to the identification of a set of 75 candidate genes (42, 22 and 11 from Arabidopsis, potato and tomato, respectively). Mapping results showed that the candidate genes were distributed on the 16 sesame linkage groups. Wide range of genes with various functions identified in this study confirmed that drought tolerance in sesame is under the control of several genes. Based on their functional classification, 2 groups of candidate genes were identified: (a) genes which protect the plant against drought effect; (b) signal transduction genes and transcription factors. Many transcription factors were retrieved including 6 AP2/ERF genes among which 3 were more expressed in drought tolerant material compared to the sensitive one and might play some important roles in drought tolerance in sesame. Our results provided genomic resources for further functional analysis and genetic engineering towards drought tolerance improvement in sesame. Key words: Sesamum indicum, candidate genes, drought tolerance, orthologous gene, whole genome.
Highlights
Sesame (Sesamum indicum L., 2n = 2x = 26) is one of the most commonly grown oilseed crops a seed production of more than 4.8 million tons worldwide in year 2013 (FAOSTAT, 2013) and has been suggested as the most ancient oil crop (Nayar and Mehra, 1970)
Drought will be a serious threat in the coming decades as the Intergovernmental Panel on Climate Change (IPCC) has concluded that elevated greenhouse gas concentrations are likely to lead to a general drying of the subtropics by the end of this century, creating widespread drought stress in agriculture (IPCC, 2007)
Many investigations have been carried out to enhance our understanding on the genetic basis of drought tolerance by using the genomics, transcriptomics and transgenesis approaches in the model plant Arabidopsis thaliana (Shinozaki et al, 2003; Jang et al, 2004, 2007; Ramirez et al, 2009; Lata et al, 2011; Harshavardhan et al, 2014)
Summary
These studies showed that the main genes involved in drought tolerance were transcription factors (TFs). The identification of drought related candidate genes in sesame will provide useful information for its improvement. Based on the sesame genome sequence recently released by Wang et al (2014), a set of candidate genes in whole genome of sesame were identified in this study through homology search of known drought associated genes from three relatives species, viz.
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