Despite being an economically important developmental process, the molecular events controlling fruit dehiscence are largely unknown. We have discovered that 2 MADS-box family members, AGLI and AGL5, ...encode functionally redundant proteins that are required for the proper development of the fruit dehiscence zone. Another MADS-box gene, FRUTTFULL (AGL8), may also be involved in setting up the dehiscence zone, as overexpression of FUL prevents fruit dehiscence. Possible interactions between AGLI, AGLS and FUL are discussed and an update of the newest members of the Arabidopsis MADS-box gene family is provided.
The formation of crown gall tumours involves the transfer of the T-DNA region of the Ti plasmid from Agrobacterium to plant cells and its subsequent integration into plant chromosomes. When ...agrobacteria are incubated with plant protoplasts or exudates of plants, the T-DNA region is circularized by recombination or cleavage and rejoining between the 25 bp terminal repeats; the formation of circular T-DNAs is thought to be one step in T-DNA transfer (Koukolikova-Nicola et al. 1985; Machida et al. 1986). We previously showed that the virulence region of the Ti plasmid is required for T-DNA circularization. In the present paper, we examined the circularization event in agrobacteria harbouring octopine Ti plasmids with mutations in various loci of the virulence region. The results clearly demonstrate that the gene(s) encoded in the virD locus are necessary for T-DNA circularization. In particular, the gene(s) present in the region proximal to the virD promoter are essential. We propose that product(s) of this gene have recombinase or endonuclease activity which specifically recognizes the 25 bp terminal repeats of T-DNA.
Members of the Brassicaceae family, including Arabidopsis thaliana and oilseed rape (Brassica napus), produce dry fruits that open upon maturity along a specialised tissue called the valve margin. ...Proper development of the valve margin in Arabidopsis is dependent on the INDEHISCENT (IND) gene, the role of which in genetic and hormonal regulation has been thoroughly characterised. Here we perform phylogenetic comparison of IND genes in Arabidopsis and Brassica to identify conserved regulatory sequences that are responsible for specific expression at the valve margin. In addition we have taken a comparative development approach to demonstrate that the BraA.IND.a and BolC.IND.a genes from B. rapa and B. oleracea share identical function with Arabidopsis IND since ethyl methanesulphonate (EMS) mutant alleles and silenced transgenic lines have valve margin defects. Furthermore we show that the degree of these defects can be fine-tuned for crop improvement. Wild-type Arabidopsis produces an outer replum composed of about six cell files at the medial region of the fruits, whereas Brassica fruits lack this tissue. A strong loss-of-function braA.ind.a mutant gained outer replum tissue in addition to its defect in valve margin development. An enlargement of replum size was also observed in the Arabidopsis ind mutant suggesting a general role of Brassicaceae IND genes in preventing valve margin cells from adopting replum identity.
Members of the Brassicaceae family, including Arabidopsis thaliana and oilseed rape (Brassica napus), produce dry fruits that open upon maturity along a specialised tissue called the valve margin. ...Proper development of the valve margin in Arabidopsis is dependent on the INDEHISCENT (IND) gene, the role of which in genetic and hormonal regulation has been thoroughly characterised. Here we perform phylogenetic comparison of IND genes in Arabidopsis and Brassica to identify conserved regulatory sequences that are responsible for specific expression at the valve margin. In addition we have taken a comparative development approach to demonstrate that the BraA.IND.a and BolC.IND.a genes from B. rapa and B. oleracea share identical function with Arabidopsis IND since ethyl methanesulphonate (EMS) mutant alleles and silenced transgenic lines have valve margin defects. Furthermore we show that the degree of these defects can be fine-tuned for crop improvement. Wild-type Arabidopsis produces an outer replum composed of about six cell files at the medial region of the fruits, whereas Brassica fruits lack this tissue. A strong loss-of-function braA.ind.a mutant gained outer replum tissue in addition to its defect in valve margin development. An enlargement of replum size was also observed in the Arabidopsis ind mutant suggesting a general role of Brassicaceae IND genes in preventing valve margin cells from adopting replum identity.
