Zeatin accumulation and misexpression of a class I knox gene are intimately linked in the epiphyllous response of the interspecific hybrid EMB-2 (Helianthus annuus x H. tuberosus).
Epiphylly, occurring in a somaclonal variant (EMB-2) of the interspecific hybrid Helianthus annuus x H. tuberosus, was used to investigate molecular and cyto-physiological mechanisms that underlie cellular fate change. EMB-2 plants are characterized by profuse proliferation of shoot- and embryo-like structures on some leaves. We addressed the putative relationship between cytokinins and knox genes in EMB-2 plants. A class I knox gene, HtKNOT1, was isolated from H. tuberosus. A high level of HtKNOT1 transcripts was detected in EMB-2 epiphyllous leaves compared to non-epiphyllous (NEP) ones. In addition, epiphylly was related to a localized increases in zeatin and N-glycosylated cytokinins. As ectopic morphogenesis proceeded, HtKNOT1 transcripts and zeatin co-localized and showed different patterns in ectopic shoot compared with embryo-like structures, consistent with the differential role of both cytokinin and knox genes in the two morphogenetic events. Notably, a massive shoot/embryo regeneration was induced in EMB-2 NEP leaves by in vitro zeatin treatment. These results clearly indicate that localized cytokinin accumulation and ectopic expression of HtKNOT1 are closely linked in the epiphylly of EMB-2 plants.
Chiappetta
Adriana
A
Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, 87030 Cosenza, Italy.
Michelotti
Vania
V
Fambrini
Marco
M
Bruno
Leonardo
L
Salvini
Mariangela
M
Petrarulo
Maria
M
Azmi
Abdelkrim
A
Van Onckelen
Harry
H
Pugliesi
Claudio
C
Bitonti
Maria Beatrice
MB
D000595:Amino Acid Sequence; D003583:Cytokinins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox; D017343:Genes, Plant; D006368:Helianthus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D006824:Hybridization, Genetic; D018519:Meristem / Q000378:metabolism; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000187:drug effects; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development; D018547:Plant Stems / Q000378:metabolism; D017422:Sequence Analysis, DNA; D015026:Zeatin / Q000378:metabolism* / Q000494:pharmacology
D003583:Cytokinins; D018398:Homeodomain Proteins; C405985:Knox1 protein, plant; D010940:Plant Proteins; D015026:Zeatin