Abstract
BackgroundThe cuticle is an important adaptive structure whose origin played a crucial role in the transition of plants from aqueous to terrestrial conditions. HvABCG31/Eibi1 is an ABCG transporter gene, involved in cuticle formation that was recently identified in wild barley (Hordeum vulgare ssp. spontaneum). To study the genetic variation of HvABCG31 in different habitats, its 2 kb promoter region was sequenced from 112 wild barley accessions collected from five natural populations from southern and northern Israel. The sites included three mesic and two xeric habitats, and differed in annual rainfall, soil type, and soil water capacity.ResultsPhylogenetic analysis of the aligned HvABCG31 promoter sequences clustered the majority of accessions (69 out of 71) from the three northern mesic populations into one cluster, while all 21 accessions from the Dead Sea area, a xeric southern population, and two isolated accessions (one from a xeric population at Mitzpe Ramon and one from the xeric ‘African Slope’ of “Evolution Canyon”) formed the second cluster. The southern arid populations included six haplotypes, but they differed from the consensus sequence at a large number of positions, while the northern mesic populations included 15 haplotypes that were, on average, more similar to the consensus sequence. Most of the haplotypes (20 of 22) were unique to a population. Interestingly, higher genetic variation occurred within populations (54.2%) than among populations (45.8%). Analysis of the promoter region detected a large number of transcription factor binding sites: 121–128 and 121–134 sites in the two southern arid populations, and 123–128,125–128, and 123–125 sites in the three northern mesic populations. Three types of TFBSs were significantly enriched: those related to GA (gibberellin), Dof (DNA binding with one finger), and light.ConclusionsDrought stress and adaptive natural selection may have been important determinants in the observed sequence variation of HvABCG31 promoter. Abiotic stresses may be involved in the HvABCG31 gene transcription regulations, generating more protective cuticles in plants under stresses.
Highlights
The cuticle is an important adaptive structure whose origin played a crucial role in the transition of plants from aqueous to terrestrial conditions
Genetic analysis of the HvABCG31 promoter sequence from five H. vulgare ssp. spontaneum populations in Israel Sequences of the HvABCG31 promoter were compared among 112 wild barley accessions from five natural populations: Mitzpe Ramon (P1; southern Israel), Dead Sea (P2; southern), "Evolution Canyon" (P3; northern), Arbel (P4; northern), and Yehudiyya (P5; northern) (Figure 1; Table 1)
We identified 22 haplotypes; all haplotype sequences were deposited in the DDBJ database with the accession numbers AB709909– AB709930
Summary
The cuticle is an important adaptive structure whose origin played a crucial role in the transition of plants from aqueous to terrestrial conditions. The sites included three mesic and two xeric habitats, and differed in annual rainfall, soil type, and soil water capacity Over their long evolutionary history, plants have evolved morphological, physiological, biochemical, and genetic traits that enable them to respond to abiotic and biotic stresses [1]. Reports on adaptive evolution in plants are numerous, but in general, specific phenotypes associated with putative adaptive events are not well understood [2,3] One such event, the origin of the cuticle covering their outermost surfaces, was a key adaptation in the transition of plants from aqueous to terrestrial conditions. Among the many genes involved in the process of cuticle formation, Eibi is the only full ABC transporter gene for releasing cuticle compounds reported in cereals It was identified in wild barley, (Hordeum spontaneum), as “HvABCG31” by analogy with the rice gene [9,10]. HvABCG31 gene was mapped and sequenced and its major function was related to cuticle secretion [10,11,12]
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