A new mutant of Arabidopsis disturbed in its roots, right-handed slanting, and gravitropism defines a gene that encodes a heat-shock factor.
A new mutant of Arabidopsis named rha1 is characterized and the gene involved cloned. In roots, the mutant shows minimal right-handed slanting, reduced gravitropic response, notable resistance to 2,4-D, but scarce resistance to IAA and NAA. The roots also show a clear resistance to the auxin transport inhibitors TIBA and NPA, and to ethylene. Other characteristics are a reduced number of lateral roots and reduced size of shoot and root in the seedlings. The gene, cloned through TAIL-PCR, was found to be a heat-shock factor that maps on chromosome 5, close to and above the RFLP marker m61. The rha1 structure, mRNA, and translation product are reported. Since, so far, no other gravitropic mutant has been described as mutated in a heat-shock factor, rha1 belongs to a new group of mutants disturbed in slanting, gravitropism, and auxin physiology. As shown through the RT-PCR analyses of its expression, the gene retains the function connected with heat shock. If the characteristics connected with auxin physiology are considered, however, it is also likely that the gene, as a transcription factor, could be involved in root circumnutation, gravitropic response, and hormonal control of differentiation. Since GUS staining under the gene promoter was localized mainly in the mature tissues, rha1 does not seem to be involved in the first steps of gravitropism, but is rather related to the general response to auxin. The alterations in slanting (mainly due to reduced chiral circumnutation) and gravitropism lead to the supposition that the two processes may have, at least in part, common origins.
Fortunati
A
A
Institute of Agroenvironmental and Forest Biology (IBAF), Consiglio Nazionale delle Ricerche, Monterotondo (Rome), Italy.
Piconese
S
S
Tassone
P
P
Ferrari
S
S
Migliaccio
F
F
D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D005030:Ethylenes / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D018522:Gravitropism; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D018869:Heat-Shock Response; D007210:Indoleacetic Acids / Q000494:pharmacology; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology*; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D005030:Ethylenes; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D007210:Indoleacetic Acids; D010940:Plant Proteins; C081080:Rha1 protein, Arabidopsis; D014157:Transcription Factors; D015084:2,4-Dichlorophenoxyacetic Acid; C036216:ethylene; D020691:rab GTP-Binding Proteins