The diageotropica Mutation and Synthetic Auxins Differentially Affect the Expression of Auxin-Regulated Genes in Tomato

Abstract

The effect of a tomato (Lycopersicon esculentum) mutation, diageotropica (dgt), on the accumulation of mRNA corresponding to tomato homologs of three auxin-regulated genes, LeAux, LeSAUR, and Lepar, was examined. The dgt mutation inhibited the induction of LeAux and LeSAUR mRNA accumulation by naphthalene acetic acid (NAA) but had no effect on NAA-induced Lepar mRNA accumulation. The effect of two synthetic auxins, NAA and 3,7-dichloro-8-quinoline carboxylic acid (quinclorac), on the accumulation of LeAux, LeSAUR, and Lepar mRNA was also examined. Quinclorac induced the expression of each of the auxin-regulated genes, confirming its proposed mode of herbicidal action as an auxin-type herbicide. Concentrations of quinclorac at least 100-fold higher than NAA were required to induce LeAux and LeSAUR mRNA accumulation to similar levels, whereas Lepar mRNA accumulation was induced by similar concentrations of NAA and quinclorac. Collectively, these data suggest the presence of two auxin-dependent signal transduction pathways: one that regulates LeSAUR and LeAux mRNA accumulation and is interrupted by the dgt mutation and a second that regulates Lepar mRNA accumulation and is not defective in dgt tomato hypocotyls. These two auxin-regulated signal transduction pathways can be further discriminated by the action of two synthetic auxins, NAA and quinclorac.

Sugar Regulates mRNA Abundance of H+-ATPase Gene Family Members in Tomato

“…Nearly equal amounts of PCR products were produced from the total RNA of NAA-treated hypocotyl and competitor RNA at 10 pg, whereas only a small amount of PCR product was produced from the total RNA of untreated hypocotyl in the presence of 10 pg of competitor RNA. The induction of LeAux mRNA accumulation by NAA treatment is consistent with our previous results (Mito and Bennett, 1995). The validity of the competitive PCR method for the quantification of plant mRNA was further confirmed by comparison of the quantification of LeAux mRNA accumulation by both northern hybridization and competitive PCR.…”

“…Hypocotyls were collected from plants grown in the dark or in the light for 4 d. Cotyledons were collected from plants grown in the light for 5 d. Mature leaves were collected from plants grown in the light for 21 d. Auxin treatment was conducted using dark-grown hypocotyls, as described elsewhere (Mito and Bennett, 1995). MS medium and sugar treatment was conducted using fully expanded cotyledons.…”

“…To confirm the effectiveness of a competitive PCR assay of RNA levels in tomato, we used the auxin-regulated LeAux gene as a standard with an expression pattern that had previously been studied in tomato (Mito and Bennett, 1995). Competitor RNA was synthesized from a partia1 genomic clone of LeAux, which was distinguishable from the LeAux mRNA because of its larger size, due to the presence of an intron.…”

“…Following reverse transcription the mixture was heated at 94°C for 5 min to denature reverse transcriptase and used for PCR amplification. AS1 (5'-CCAGGGAGGACAGATGA-3') and AS2 (5'-CAAGCATCAAGTCACCA-3') primers for LeAux, corresponding to nucleotides 21 to 39 and 418 to 436 of a previously published partia1 sequence (Mito and Bennett, 1995), and 1-a, 1-b, 2-a, 2-b, 4-a, and 4-b primers for H fATPase amplification were used. Amplifications were carried out in a final volume of 50 pL containing PCR buffer (50 mM KC1, 10 mM Tris-HC1 [pH 91, 1.5 mM MgC1, 0.01% [w/w] gelatin, 0.1% [v/v]) Triton X-100, 0.2 mM each deoxyribonucleotide triphosphate, 25 pmol of each primer, and 0.25 unit of DNA polymerase for 30 cycles with denaturation for 1 min at 94"C, annealing for 2 min at 55°C for LeAux and 58°C for H+-ATPases and extension for 2 min at 72°C.…”

Controle do desenvolvimento vegetal pela interação auxina-citocinina. Uma nova abordagem baseada no estudo de mutantes de tomateiro (Solanun lycopersicum cv Micro-Tom)

“…Em alguns frutos, auxinas induzem o pegamento e o crescimento destes (SERRANI et al, 2007). Auxinas regulam ainda a partição de assimilados (LENTON, 1984), promovem atraso no amadurecimento de frutos (DAVIES; BOSS; ROBINSON, 1997), promovem o florescimento em algumas espécies (SALISBURY, 1955) e estimulam o crescimento de alguns órgãos florais (BENNETT et al, 1995;NEMHAUSER;FELDMAN;ZAMBRYSKI, 2000;OKADA et al, 1991;VERNOUX et al, 2000).…”