In Erwinia chrysanthemi, conditions of iron starvation initiate production of a catechol-type siderophore and enhance production of three outer membrane polypeptides. Twenty-two mutants affected in the different stages of this iron assimilation system were isolated by mini-Mu insertion mutagenesis. All of them failed to induce systemic soft rot on axenically grown Saintpaulia plants. From the siderophore auxotrophs and the iron uptake mutants, clones having recovered the missing function(s) were isolated by using the in vivo cloning vector pULB113 (RP4::mini-Mu). An R-prime plasmid containing a ca. 35.5-kilobase-pair DNA insert was identified. Restoration of the iron functions restored partially, if not completely, the virulence of the parental strain.

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Erwinia chrysanthemi 3937 secretes four major pectate lyase isoenzymes (PL, EC 4.2.2.2) and one endocellulase (Cx, EC 3.2.1.4). A genomic library of this strain was constructed in the Lambda L47‐1 vector, and screened for the presence of PL and Cx on pectate and caboxymethylcellulose agar. Among the seven Cx‐positive phage clones, three were shown to encode an enzyme of the same mol. wt. as the one found in the culture supernatant of strain 3937. The 34 PL‐positive phage clones were analyzed by electrofocusing and could, according to the PL they produced, be arranged in five classes. Phages from three classes produced three different single PL, named PLb, c and d. No common fragment was evidenced between the inserts of the phages of these three classes. This demonstrated that, in strain 3937, PLb, C, and d were encoded by three different genes called pelB, C, and D. Furthermore, our results suggest the existence of two additional genes encoding PLa and e. In addition, a pectin methylesterase gene was found closely linked to pelD.

The phytopathogenic fungus Botrytis cinerea can infect an extremely wide range of host plants (tomato, grapevine, strawberry, and flax) without apparent specialization. While studying genetic diversity in this fungus, we found an element which is present in multiple copies and dispersed throughout the genome of some of its isolates. DNA sequence analysis revealed that the element contained direct, long-terminal repeats (LTRs) of 596 bp whose features were characteristic of retroviral and retrotransposon LTRs. Within the element, we identified an open reading frame with sequences homologous to the reverse transcriptase and RNase H domains of retroelement pol genes. We concluded that the element we had identified was a retroelement and named it Boty. By comparing its open reading frame with sequences from other retroelements, we found that Boty is related to the gypsy family of retrotransposons. Boty was present in numerous strains isolated from grapes and tomatoes but not in isolates from lentils. We propose that Boty-containing and Boty-deficient groups represent two lineages in the population of B. cinerea.

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