Tomato (Lycopersicon esculentum) Genomic Clone Homologous to a Gene Encoding an Abscisic Acid-Induced Protein

The plant hormone ABA is involved in a number of important physiological and developmental processes including the response of vegetative tissues to osmotic stress and fruit ripening (Davies and Mansfield, 1983). We report here the main structural features of a gene termed Asr2 (Table I), homologous to Asrl (standing for ABA, stress, and ripening), whose cDNA has been previously characterized (Iusem et al., 1993). Asrl is induced by ABA, water deficit, and ripening as demonstrated by independent hybridization with RNA from water-deficit and ABA-induced plants as well as RNA from immature, mature, and ripe fruit (our unpublished results). The genomic sequence reported here contains 935 nucleotides, starting 131 nucleotides upstream of the translation initiation codon. Two exons were identified: one comprising nucleotides 132 to 290 and another between nucleotides 402 and 551; these were separated by an intervening sequence. The coding region shows 73% homology with the Asrl cDNA sequence, resulting in an overall homology of 85% at the protein level. This probably indicates that Asrl and Asr2 are different members of a gene family. This gene family enlarges the list of the known ABAresponsive genes (Skriver and Mundy, 1990). Further sequencing of upstream regions from Asr2 will enable us to identify 5’ regulatory elements involved in ABA-mediated responses in tomato. In monocots, cis-regulatory elements have been demonstrated to be functional in ABA-responsive genes from wheat (Marcotte et al., 1989), rice (Mundy et al., 1990), and maize (Vilardell et al., 1991). In some cases, those elements helped characterize specific nuclear DNA-binding proteins that mediate responses to ABA (Guiltinan et al., 1990; Mundy et al., 1990; Pla et al., 1993). It is interesting that the product of Asrl itself is a nuclear basic protein that binds DNA (P.A. Scolnik, unpublished results from southwestern and filter-binding experiments done with the protein overexpressed in Escherichia coli) and therefore might, in tum, modulate gene expression. Confirrning the universality of suggested consensus motifs involved in ABA responses such as CCACGTGG (Pla et al., 1993), as well as the finding of new genomic regulatory