Characterization of Cestrum yellow leaf curling virus: a new member of the family Caulimoviridae.
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Cestrum yellow leaf curling virus (CmYLCV) has been characterized as the aetiological agent of the Cestrum parqui mosaic disease. The virus genome was cloned and the clone was proven to be infectious to C. parqui. The presence of typical viroplasms in virus-infected plant tissue and the information obtained from the complete genomic sequence confirmed CmYLCV as a member of the Caulimoviridae family. All characteristic domains conserved in plant pararetroviruses were found in CmYLCV. Its genome is 8253 bp long and contains seven open reading frames (ORFs). Phylogenetic analysis of the relationships with other members of the Caulimoviridae revealed that CmYLCV is closely related to the Soybean chlorotic mottle virus (SbCMV)-like genus and particularly to SbCMV. However, in contrast to the other members of this genus, the primer-binding site is located in the intercistronic region following ORF Ib rather than within this ORF, and an ORF corresponding to ORF VII is missing. (+info)
Differential effects of NAA and 2,4-D in reducing floret abscission in cestrum (Cestrum elegans) cut flowers are associated with their differential activation of Aux/IAA homologous genes.
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BACKGROUND AND AIMS: A previous study showed that the relative effectiveness of 2,4-dichlorophenoxyacetic acid (2,4-D) compared with that of 1-naphthaleneacetic acid (NAA) in reducing floret bud abscission in cestrum (Cestrum elegans) cut flowers was due to its acropetal transport. The aim of the present study was to examine if the differential effect of these auxins on floret abscission is reflected in the expression of Aux/IAA genes in the floret abscission zone (AZ). METHODS: cDNAs were isolated by PCR-based cloning from the floret AZ of auxin-treated cut flowers. The expression patterns of the cDNAs in various tissues and the effect of indole-3-acetic acid (IAA), applied with or without cycloheximide, on their expression in the floret AZ were examined by northern blot analysis. The regulation of transcript accumulation in the floret AZ in response to NAA or 2,4-D was measured by real-time PCR during auxin pulsing of cut flowers and vase life, concomitantly with floret abscission. KEY RESULTS: Six isolated cDNAs were identified to represent Aux/IAA homologous genes, designated as Cestrum elegans (Ce)-IAA1 to Ce-IAA6. Four Ce-IAA genes were characterized as early auxin-responsive genes (ARGs), and two (Ce-IAA1 and Ce-IAA5) as late ARGs. Only Ce-IAA5 was AZ-specific in floret buds. A temporal regulation of Ce-IAA transcript levels in the floret AZ was found, with 2,4-D inducing higher expression levels than NAA in floret buds. These Ce-IAA expression levels were negatively correlated with floret abscission. CONCLUSIONS: The differential transport characteristics of NAA and 2,4-D in cestrum cut flowers were reflected in differential activation of the Ce-IAA genes identified in the floret AZ. Therefore, Aux/IAA genes can be used as molecular markers to measure auxin activity, which reflects free auxin level in the AZ. Two of the identified genes, Ce-IAA1 and Ce-IAA5, may also have a regulatory role in abscission. (+info)
The Drosophila flavopilosa species group (Diptera, Drosophilidae): an array of exciting questions.
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