A biotype of Amaranthus retro¯exus L. is the ®rst weed in Israel to develop resistance to acetolactate synthase (ALS)-inhibiting herbicides. The resistant biotype (Su-R) was collected from Ganot, a site that had been treated for more than 3 consecutive years with sulfometuronmethyl + simazine. On the whole-plant basis, the resistance ratio (ED 50 Su-R)/(ED 50 Su-S) was 6±127 for sulfonylureas, 4±63 for imidazolinones, 20±35 for triazolopyrimidines and 11 for pyrithiobac-sodium. Similar levels of resistance were found also when the herbicides were applied before emergence. Based on a root elongation bioassay, Su-R was 3240-fold more resistant to sulfometuron-methyl than Su-S. In vitro studies have shown that the Su-R biotype was resistant at the enzyme level to all ALS inhibitors tested. The nucleotide sequences of two ampli®ed regions between the Su-S and the Su-R diered in only one nucleotide. One substitution has occurred in domain A, cytosine by thymine (CCC to CTC) at position 248, that confers an exchange of the amino acid proline in the susceptible to leucine in the Su-R 1. The proline to leucine change in domain A is the only dierence in the amino acid primary structure of the regions sequenced, indicating that it is responsible for the ALS-inhibitor resistance observed.

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Seven cDNA clones of Schistosoma mansoni containing the C-terminal part of the deduced sequence of a mucin-like protein have been identified. The protein contains 28% threonines, 20% serines, and has a pI of 3.4. On Northern blots of RNA of adult worms, the cDNA clones detect 2 transcripts of 1.65 and 4.2 kb which are expressed only in female worms. The tissue of gene expression, as revealed by in situ hybridization, is the epithelium surrounding the female reproduction duct proximal to its entrance into the ootype. Accumulation of N-glycosylation sites suggests that the protein, like other mucins, might form a protective layer, coating the lining of the duct. Regarding its acidic pI, we hypothesize a role in preventing premature egg-shell formation. This is the first female-specifically transcribed sequence, hitherto known in S. mansoni that is not expressed in the vitellaria.

Schistosomu mansoni possesses two isoforms of ferritin, soma and yolk ferritin. The soma ferritin occurs at a low level in most cells of both genders, whereas the yolk ferritin is a female-specific gene product that is expressed at high level in the vitellarium. In higher animals, ferritin mRNA is regulated by iron via the interaction of cytoplasmic binding proteins (IRPs) with a specific sequence element in the 5' untranslated region (UTR) referred to as the iron-responsive element (IRE). Sequence studies of the 5' UTRs, gel retardation assays, and hybridization experiments show that neither ferritin mRNAs of S. rnansoni is regulated by an IRE/IRP mechanism. It is suggested that ferritins in schistosomes are controlled only at the transcriptional level.

A female-specific sequence was isolated from a cDNA library of Schistosoma mansoni and further characterized. Expression of the corresponding gene (p19) depends on pairing with a male. In situ hybridization and immunohistology experiments revealed exclusive expression of the gene in the cells of the vitellarium, suggesting a function in egg formation. In addition, experimental evidence for cross-linking of the protein under oxidative conditions supports the assumption that the p19 gene may code for an egg-shell precursor protein.