Pectins are essential components of primary plant cell walls and middle lamellae, and are related to the consistency of the fruit and its textural changes during ripening. In fact, strawberries become soft as the middle lamellae of cortical parenchyma cells are extensively degraded during ripening, leading to the observed short post-harvest shelf life. Using a custom-made oligonucleotide-based strawberry microarray platform, a putative rhamnogalacturonate lyase gene (FaRGlyase1) was identified. Bioinformatic analysis of the FaRGlyase1 sequence allowed the identification of a conserved rhamnogalacturonate lyase domain, which was also present in other putative RGlyase sequences deposited in the databases. Expression of FaRGlyase1 occurred mainly in the receptacle, concurrently with ripening, and it was positively regulated by abscisic acid and negatively by auxins. FaRGLyase1 gene expression was transiently silenced by injecting live Agrobacterium cells harbouring RNA interference constructs into fruit receptacles. Light and electron microscopy analyses of these transiently silenced fruits revealed that this gene is involved in the degradation of pectins present in the middle lamella region between parenchymatic cells. In addition, genetic linkage association analyses in a strawberry-segregating population showed that FaRGLyase1 is linked to a quantitative trait loci linkage group related to fruit hardness and firmness. The results showed that FaRGlyase1 could play an important role in the fruit ripening-related softening process that reduces strawberry firmness and post-harvest life.

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In Europe, 18 weedy grass species had been confirmed to have biotypes with resistance to herbicides. The most frequent is that of atrazine resistance, with nine resistant biotypes found. These biotypes are mainly resistant because of changes in the D1 protein of photosystem II. All atrazine-resistant biotypes, except that of bristly foxtail, show cross-resistance to s-triazine and as-triazines. From an agriculture point of view, the most important cases of resistance are those found in blackgrass, wild oat, Italian ryegrass, rigid ryegrass, and barnyardgrass. In these species, cross- and multiple resistances were observed due to metabolism or changes in the target protein by genetic mutations or both. These biotypes are extremely difficult to control with alternative herbicides.

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A strain of Chlamydomonas reinhardtii, named ARF-1, which grows with the glutamine synthetase (CS) inhibitor i-methionine-S sulfoximine (MSX), has been isolated and characterized. Mutant ARF-1 i s affected a t a single and dominant gene, tentatively assigned t o the allele msr-1-2. Neither the uptake of ammonia nor the two CS isoenzyme activities of the mutant were affected by M S X in vivo. CS activities, however, were fully abolished in vitro, thus suggesting that neither CS isoform was an altered enzyme resistant to the inhibitor. Resistance to MSX does not seem t o be due t o either a defect in a permease responsible for the transport of M S X or overexpression of CS activity, nor did we find an alternative enzymatic pathway for the assimilation of ammonium. Resistance was independent of the nitrogen source used and was strongly enhanced by the addition of acetate. Unlike the parental strain, mutant ARF-1 can degrade and utilize MSX as the sole nitrogen source for growth, which could account for the observed resistance. Thus, this mutant can be classified as a nove1 type of MSX-resistant mutant. This mutant can also use phosphinothricin, methionine sulfone, or methionine sulfoxide as the sole sources of nitrogen. This capability cosegregated in the genetic crosses and was also observed in all the diploids isolated. An MSX/cu-ketoglutarate aminotransferase activity, not present in the parental strain 305, was detected i n mutant ARF-1 cells. Therefore, we propose that the locus msr-7-2 either codes for this transaminase activity or i t s product gene is necessary to express this transaminase activity.