Differential expression of plastidic aldolase genes in Nicotiana plants under salt stress

Two homologous genes of plastidic fructose-1,6-bisphosphate aldolase (AldP) isozymes were isolated from green leaves of a salt stress-tolerant Nicotia na species, Nicotiana paniculata, by differential screening. The products o f the corresponding genes, NpAldP1 and NpAldP2, were 91% identical to each other and 70-85% identical to the other known plant plastidic aldolases. Al though these two genes showed similar organ-specific expression and daily c ycles, their responses to salt stress differed: mRNA accumulation of NpAldP 2 increased, but that of NpAldP1 slightly decreased. The mRNA accumulations of their counterparts of two other Nicotiana species, NeAldP1 and NeAldP2 (Nicotiana excelsior), and NaAldP1 and NaAldP2 (Nicotiana arentsii) were st udied under the same stress condition. N. arentsii conserved accumulation p rofiles similar to N. paniculata, but N. excelsior did not. In N. excelsior , accumulation of NeAldP1 decreased to 50% of the control after stress and gradually recovered thereafter, whereas accumulation of NeAldP2 temporarily decreased and reached 250% of the control by the third day of stress. Sout hern blot analysis indicated that NpAldP1, NpAldP2, NaAldP1, and NaAldP2 in clude one or two closely related genes and NeAldP1 and NeAldP2 several. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.