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Insight into the AP2/ERF transcription factor superfamily in sesame and expression profiling of DREB subfamily under drought stress

Komivi Dossa1,2,3, Xin Wei1, Donghua Li1, Daniel Fonceka2,4, Yanxin Zhang1, Linhai Wang1, Jingyin Yu1, Liao Boshou1, Diaga Diouf3, Ndiaga Cissé2 and Xiurong Zhang1*

Abstract

Background : Sesame is an important oilseed crop mainly grown in inclement areas with high temperatures and
frequent drought. Thus, drought constitutes one of the major constraints of its production. The AP2/ERF is a large
family of transcription factors known to play significant roles in various plant processes including biotic and abiotic
stress responses. Despite their importance, little is known about sesame AP2/ERF genes. This constitutes a limitation
for drought-tolerance candidate genes discovery and breeding for tolerance to water deficit.

Results : One hundred thirty-two AP2/ERF genes were identified in the sesame genome. Based on the number of
domains, conserved motifs, genes structure and phylogenetic analysis including 5 relatives species, they were
classified into 24 AP2, 41 DREB, 61 ERF, 4 RAV and 2 Soloist. The number of sesame AP2/ERF genes was relatively
few compared to that of other relatives, probably due to gene loss in ERF and DREB subfamilies during
evolutionary process. In general, the AP2/ERF genes were expressed differently in different tissues but exhibited the
highest expression levels in the root. Mostly all DREB genes were responsive to drought stress. Regulation by
drought is not specific to one DREB group but depends on the genes and the group A6 and A1 appeared to be
more actively expressed to cope with drought.

Conclusions : This study provides insights into the classification, evolution and basic functional analysis of AP2/ERF
genes in sesame which revealed their putative involvement in multiple tissue-/developmental stages. Out of 20 genes
which were significantly up- /down-regulated under drought stress, the gene AP2si16 may be considered as potential
candidate gene for further functional validation as well for utilization in sesame improvement programs for drought
stress tolerance.

Keywords : Sesamum indicum, AP2/ERF, Transcription factors, Gene expression, Drought stress