Iron deficiency-mediated stress regulation of four subgroup Ib BHLH genes in Arabidopsis thaliana

• Published in: Planta Vol. 226; no. 4; pp. 897 - 908
• Main Authors: Wang, Hong-Yu, Klatte, Marco, Jakoby, Marc, Bäumlein, Helmut, Weisshaar, Bernd, Bauer, Petra
• Format: Journal Article
• Language: English
• Published: Berlin Berlin/Heidelberg : Springer-Verlag 01.09.2007; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Adaptation, Physiological; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Basic helix-loop-helix; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; bHLH; Biological and medical sciences; Cell physiology; DNA, Bacterial; Exons; Fer-like iron-deficiency induced transcription factor (FIT); Fundamental and applied biological sciences. Psychology; Gene expression; Gene expression regulation; Gene Expression Regulation, Plant; Gene induction; Genes; Genes, Reporter; Glucuronidase - genetics; Glucuronidase - metabolism; Iron; Iron - metabolism; Iron acquisition; Iron uptake; Leaves; Molecular and cellular biology; Mutagenesis, Insertional; Phenotype; Plant Leaves - metabolism; Plant roots; Plant Roots - metabolism; Plants; Promoter Regions, Genetic; Proteins; Signal transduction; Split root; Transcription factor; Transcription factors; Up regulation; Zinc; Root; Iron acquisition; Basic helix-loop-helix; Stress; bHLH; Arabidopsis thaliana; Split root; Gene; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Fer-like iron-deficiency induced transcription factor (FIT); Transcription factor; Iron uptake
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-007-0535-x

Networks of transcription factors control physiological, developmental and environmental responses. Root iron acquisition responses are controlled by the essential bHLH protein FIT. Recently, two group Ib BHLH genes were reported to be iron deficiency-regulated. Here, we studied expression patterns of these two group Ib BHLH genes and of their two closest homologs to analyze whether their regulation would support a function in iron deficiency responses. We found that BHLH038, BHLH039, BHLH100 and BHLH101 (comprising a subgroup of BHLH Ib genes) were up regulated by iron deficiency in roots and leaves. Single insertion mutants had no visible phenotype and were capable of inducing root iron acquisition responses, presumably due to functional redundancy. Specific metal treatments like nickel, high zinc or high copper resulted in induction of the four BHLH Ib genes whereas high iron, low copper and low zinc repressed gene expression. Induction of the four BHLH Ib genes was also found in multiple iron acquisition mutants including fit. Ectopic activation of FIT did not suppress the four BHLH Ib genes. Split-root analyses using promoter-GUS lines showed that FIT and BHLH100 promoters were controlled by different local and systemic signals involved in their regulation by iron. These results indicated that the four BHLH Ib genes were induced independently from FIT by conditions causing iron deficiency. Taken together, BHLH038, BHLH039, BHLH100 and BHLH101 function differently from FIT and may be involved in mediating a signal related to iron deficiency-induced stress and/or internal iron homeostasis.