Abstract
Homeodomain-leucine zipper (HD-Zip) gene family plays important roles in various abiotic stresses and hormone signaling in plants. However, no information is currently available regarding this family in cassava (Manihot esculenta), an important drought-tolerant crop in tropical and sub-tropical areas. Here, 57 HD-Zip genes (MeHDZ01-57) were identified in the cassava genome, and they were classified into four subfamilies based on phylogenetic analysis, which was further supported by their gene structure and conserved motif characteristics. Of which five gene pairs were involved in segmental duplication but none for tandem duplication, suggesting that segmental duplication was the main cause for the expansion of MeHDZ gene family in cassava. Global expression profiles revealed that MeHDZ genes were constitutively expressed, or not expressed, or tissue-specific expressed in examined tissues in both cultivated and wild subspecies. Transcriptomic analysis of three genotypes showed that most of MeHDZ genes responded differently to drought and polyethylene glycol treatments. Subsequently, quantitative RT-PCR analysis revealed comprehensive responses of twelve selected MeHDZ genes to various stimuli including cold, salt, and ABA treatments. These findings will increase our understanding of HD-Zip gene family involved in abiotic stresses and signaling transduction, and will provide a solid base for further functional characterization of MeHDZ genes in cassava.
Highlights
Homeodomain-leucine zipper (HD-Zip) proteins are one of key transcription factors in plants
This phenomenon was observed in each subfamily, e.g., subclass a, f, i in subfamily I, subclass m, p in subfamily II, subclass t in subfamily III, and subclass D in subfamily IV; (2) HD-Zip genes that were generated before the divergence of eudicots and monocots but their homologs in some speices might be lost during the evolution, because they were presented in both eudicots and monocots but not in all of examined species, e.g., subclass j, k in subfamily II, subclass q, r in subfamily III, and subclass u, w in subfamily IV; (3) HD-Zip genes that were generated after the divergence of eudicots and monocots, as they were exclusively presented in eudicots
They were either highly conserved or not very conserved; (4) HD-Zip genes that were generated after the divergence of eudicots and monocots, but they were exclusively presented in monocots
Summary
Homeodomain-leucine zipper (HD-Zip) proteins are one of key transcription factors in plants. HD-Zip proteins were characterized by the presence of two functional domains: a homeodomain (HD) responsible for specific binding to DNA and a leucine zipper (LZ) motif which closely linked to HD and acted as a dimerization motif [1,2]. Many members of HD-Zip proteins have been found in a large number of plant species, including Arabidopsis [3], rice [4], maize [5], soybean [6], legume [7], banana [8], and so on. HD-Zip proteins were mainly categorized into four groups: HD-Zip I.
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