Auxin-induced gene expression in mesocotyl elongation of maize inbred line 3681-4 tolerant to deep-sowing

In order to elucidate the molecular mechanism of auxin-induced mesocotyl elongation, gene expression profiling analyses were performed in a deep-sowing tolerant maize inbred line 3681-4. Gene expression studies combing Affymetrix GeneChip analysis and Real-time PCR were employed to determine the molecular mechanism underlying IAA promotion of maize mesocotyl elongation. Under deep-sowing condition, IAA is transported by auxin transporter-like protein 1 and binds to auxin binding protein ABP20, which results in degradation of Aux/IAA and de-repressing of auxin-inducible genes. Then, transcriptional factor such as MYB, kinase such as LRR, fructose and mannose metabolism and so on are activated. Finally, genes involved in cell wall synthesis and modification are expressed so that mesocotyl elongation of 3681-4 is promoted. Furthermore, gene expression of a key enzyme ACO in ethylene biosynthesis and ethylene receptor ETR2 were up-regulated after the treatment with 10-4 M IAA, which suggested that mesocotyl elongation of 3681-4 inclined to be inhibited when the concentration of applied IAA was increased from 10-4 M to 10-3 M. In two independent experiments, we generate 10-day-old maize mesocotyl-specific gene expression profiles through comparing genome-wide expression patterns of IAA treatment and TIBA (an auxin transportation inhibitor) treatment under 20 cm deep-sowing condition in darkness by using 17,555 Affymetrix maize whole genome array.