Abstract
BackgroundThe ability of plants to withstand and thrive in an adverse environment is crucial to ensure their survivability and yield performance. The WRKY transcription factors (TFs) have crucial roles in plant growth, development and stress response, particularly drought stress. In oil palm, drought is recognized as one of the major yield limiting factors. However, the roles of WRKY TFs in the drought response of oil palm is unclear.ResultsHerein, we studied the transcriptome of drought treated oil palm leaf and identified 40 differentially expressed genes (DEGs) of WRKY TFs, of which 32 DEGs were upregulated and 8 DEGs were downregulated in response to drought stress in oil palm. They were categorized into Groups I to IV based on the numbers of WRKY domain and the structural difference in the zinc finger domain. Multiple stress- and hormone-responsive cis-regulatory elements were detected in the drought responsive oil palm EgWRKY (Dro-EgWRKY) genes. Fourteen of the 15 selected oil palm WRKY (EgWRKY) genes demonstrated a tissue-specific expression profile except for EgWRKY28 (Group I), which was expressed in all tissues tested. The expression levels of 15 candidate EgWRKYs were upregulated upon salinity and heat treatments, while several genes were also inducible by abscisic acid, methyl jasmonate, salicylic acid and hydrogen peroxide treatments. Members of the Group III WRKY TFs including EgWRKY07, 26, 40, 52, 59, 73 and 81 displayed multiple roles in drought- and salinity-response under the modulation of phytohormones.ConclusionsEgWRKY TFs of oil palm are involved in phytohormones and abiotic stress responses including drought, salinity and heat. EgWRKY07, 26, 59 and 81 from Group III maybe important regulators in modulating responses of different abiotic stresses. Further functional analysis is required to understand the underlying mechanism of WRKY TFs in the regulatory network of drought stress.
Highlights
The ability of plants to withstand and thrive in an adverse environment is crucial to ensure their surviv‐ ability and yield performance
Identification of Dro‐EgWRKY genes from the transcriptome of drought‐treated oil palms To elucidate the roles of transcription factors (TFs) in drought response, we first identified the TFs among the differential expressed genes (DEGs) identified from the RNA-Seq study on oil palm treated with drought stress in comparison to untreated control oil palm
A total of 6998 DEGs were identified from the RNA-seq analysis; whereby 4175 DEGs were upregulated and 2823 DEGs were downregulated in response to drought stress (Fig. 1A)
Summary
The ability of plants to withstand and thrive in an adverse environment is crucial to ensure their surviv‐ ability and yield performance. The WRKY transcription factors (TFs) have crucial roles in plant growth, development and stress response, drought stress. Drought is recognized as one of the major yield limiting factors. The roles of WRKY TFs in the drought response of oil palm is unclear. WRKY protein is one of the largest transcription factor (TF) family found in the plant kingdom. The zinc finger structure can be divided based on the C2H2 motif (C-X4-5-C-X22-23-H-X1-H) and the C2HC motif (C-X5-7-C-X2-3-H-X1-C) [4]. The WRKY proteins are categorized into three groups based on the number of WRKY domains and the zinc finger binding motifs. Group I and II members share the same C2H2-type zinc finger motif while Group III members have the C2HC-type. Group II members can be divided into five subgroups based on their phylogenetic relationships [6]
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