~Osmotin-like proteins are encoded by at least six members of a multigene family in Solanum commersonii. A genomic clone (ApCEM2a-7) that contains two osmotin-like protein genes (OSML13 and OSML81) arranged in the same transcriptional orientation has been isolated. Restriction mapping and sequence analysis indicated that the two intronless genes correspond to the previously characterized pA13 and pA81 cDNAs. To study the transcriptional activation of OSMLl3 and OSML8l promoters, the 5' flanking DNA sequence (-1078 to +35 of OSML13 and -1054 to +41 of OSML81) was fused to the p-glucuronidase (CUS) coding region, and the chimeric gene fusions were introduced into wild potato (S. commersonii) plants via Agrobacferiummediated transformation. Analysis of the chimeric gene expression in transgenic potato plants showed that both 5' flanking DNA sequences are sufficient to impart CUS inducibility by abscisic acid, NaCI, salicylic acid, wounding, and fungal infection. Low temperature activated both chimeric genes only slightly. lnfection with Phyfophthora infestam resulted in strong CUS expression from both chimeric genes primarily i n the sites of pathogen invasion, suggesting a limited diffusion of fungal infection-mediated signals. The expression patterns of both osmotin-like protein genes implicate their dual functions in osmotic stress and plant pathogen defense.

This paper examines the effect of prior high-temperature exposure on the susceptibility of rice (cv. Kirara 397) seedlings to chilling injury, and evaluates the changes in L-ascorbate peroxidase (APX) activity and induction of transcription after exposure to high temperature in order to determine the possible role of APX in increasing the chilling tolerance to plants previously subjected to high temperature. The heat-inducible apx gene promoter sequences are characterized and chilling tolerance of transgenic rice with elevated levels of APX are examined.