Expression of ornithine decarboxylase is transiently increased by pollination, 2,4-dichlorophenoxyacetic acid, and gibberellic acid in tomato ovaries

Abstract

A cDNA encoding for a functional ornithine decarboxylase has been isolated from a cDNA library of carpels of tomato (Lycopersicon esculentum Mill.). Ornithine decarboxylase in tomato is represented by a single-copy gene that we show to be up-regulated during early fruit growth induced by 2,4-dichlorophenoxyacetic acid and gibberellic acid.

Figure 1

Alignment of the amino acid sequence derived from the clone pD12 with the ODCs from thorn-apple (Datura) (X87847), tobacco (D89984), Saccharomyces cerevisiae (Scerevisiae) (J02777), D. melanogaster (Drosophila) (X66599), and human (M16650). The sequences were aligned using the CLUSTALW program (Thompson et al., 1994). Identical amino acids in at least four different sequences are outlined in black, and conserved changes are outlined in gray.

Figure 2

A, Southern-blot analysis of tomato genomic DNA. Genomic DNA (30 μg) was digested with: lane 1, DraI; lane 2, EcoRV; lane 3, AccI; lane 4, HincII; and lane 5, XbaI. B, Copy-number reconstruction experiment. Thirty micrograms of genomic DNA digested with DraI was loaded in the first lane (DraI); lanes 2 through 4 correspond to different amounts of the linearized pD12 plasmid representing one, two, and four copies per haploid genome in 30 μg of genomic DNA. The blots were hybridized with the entire ODC clone. Size markers are indicated.

Figure 3

Northern analysis of ODC gene expression in naturally pollinated ovaries. Ovaries were collected at −1 (lane U-1), 2 (lane P2), 5 (lane P5), 8 (lane P8), and 12 (lane P12) DPA. Twenty micrograms of total RNA was loaded per lane.

Figure 4

Analysis of ODC mRNA levels in unpollinated ovaries treated with 2,4-D or with GA₃ or untreated (control). Treatments were made at −1 DPA. Numbers indicate the age of the ovaries. Twenty micrograms was loaded per lane.

Figure 5

Analysis of ODC mRNA accumulation in different organs and tissues of tomato plants. T, Shoot tips; L, leaves; F, whole flowers at anthesis; R, roots; and S, stem. Twenty-five micrograms of total RNA was loaded per lane.