The effect of ABA analogs on callus viability and gene expression in Craterostigma plantagineum

The majority of flowering-plant species can survive complete air-dryness in their seed and/or pollen. Relatively few species (‘resurrection plants’) express this desiccation tolerance in their foliage. Knowledge of the regulation of desiccation tolerance in resurrection plant foliage is reviewed. Elucidation of the regulatory mechanism in resurrection grasses may lead to identification of genes that can improve stress tolerance and yield of major crop species. Well-hydrated leaves of resurrection plants are desiccation-sensitive and the leaves become desiccation tolerant as they are drying. Such drought-induction of desiccation tolerance involves changes in gene-expression causing extensive changes in the complement of proteins and the transition to a highly-stable quiescent state lasting months to years. These changes in gene-expression are regulated by several interacting phytohormones, of which drought-induced abscisic acid (ABA) is particularly important in some species. Treatment with only ABA induces desiccation tolerance in vegetative tissue of Borya constricta Churchill. and Craterostigma plantagineum Hochstetter. but not in the resurrection grass Sporobolus stapfianus Gandoger. Suppression of drought-induced senescence is also important for survival of drying. Further research is needed on the triggering of the induction of desiccation tolerance, on the transition between phases of protein synthesis and on the role of the phytohormone, strigolactone and other potential xylem-messengers during drying and rehydration.

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Differences in LEA-like 11-24 gene expression in desiccation tolerant and sensitive species of Linderniaceae are due to variations in gene promoter sequences

Functional Plant Biology ◽

10.1071/fp15238 ◽

2016 ◽

Vol 43 (7) ◽

pp. 695 ◽

Cited By ~ 2

Author(s):

Saeedeh Ataei ◽

Verena Braun ◽

Dinakar Challabathula ◽

Dorothea Bartels

Keyword(s):

Gene Expression ◽

Particle Bombardment ◽

Gene Promoter ◽

Transcript Abundance ◽

Late Embryogenesis Abundant ◽

Site Directed Mutagenesis ◽

Sensitive Species ◽

Craterostigma Plantagineum ◽

Underlying Mechanisms ◽

Transformation Methods

Many desiccation induced late embryogenesis abundant (LEA) protein encoding genes have been identified from Craterostigma plantagineum Hochst. In the desiccation tolerant plants C. plantagineum (Cp) and Lindernia brevidens Skan (Lb) transcripts encoding LEA-like 11-24 protein are abundantly expressed during desiccation whereas in Lindernia subracemosa De Wild. (Ls), a desiccation sensitive plant, the LEA-like 11-24 transcripts are expressed at a low level. Since promoters determine gene expression, a comparative promoter analysis was carried out to decipher the underlying mechanisms of differential gene expression. Two transient transformation methods (particle bombardment and optimised Agrobacterium co-cultivation) were used to analyse the promoter activities of the Cp, Lb and Ls LEA-like 11-24 gene in homologous and heterologous systems. Minimal promoters were isolated from all three species and their promoter activities were assessed in response to mannitol or ABA. Particle bombardment or Agrobacterium co-cultivation yielded similar results. Site-directed mutagenesis was used to identify which cis-acting elements in the LEA-like 11-24 promoter fragments are crucial during mannitol and ABA treatments. The presence of these promoter cis-elements explains the differences in transcript abundance in the desiccation tolerant and desiccation sensitive species. Results indicated the importance of the drought responsive elements (DRE) element for promoter activity.

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