Effect of long-chained auxin conjugates on gene expression in the seedlings of Brassica rapa

Auxin amino acid conjugates are considered storage forms of auxins available as a source of active auxins on the plant demand. We treated Brassica rapa seedlings with 0.01 mM indole-3-acetyl-L-alanine (IAA-Ala), indole-3-propionyl-L-alanine (IPA-Ala), and indole- 3-butyryl-L-alanine (IBA-Ala) and examined their effects on the transcriptome. All auxin conjugate treatments caused similar patterns in transcription profiles compared to the control, but with different intensities of over- and under-expression depending on the treatment. Most auxin-related DEGs were identified after IBA-Ala treatment, followed by IPA-Ala and IAA-Ala, respectively. Overall design: Seeds of Chinese cabbage (Brassica rapa L. ssp. pekinensis (Lour.) Hanelt cv. Cantonner Witkrop) were sterilized and germinated, and the 1-day-old seedlings were placed on 1 % agar plates, supplemented with the hormones indole-3-acetyl-L-alanine (IAA-Ala), indole-3-propionyl-L-alanine (IPA-Ala) or indole-3-butyryl-L-alanine (IBA-Ala) in 0.01 mM concentration. Seedlings on hormone-free agar plates were used as a control. Following incubation of the seedlings under continuous light for a further 24 h at 22 °C, total RNA was isolated from 100 mg of whole seedlings. Two biological replicates per treatment were sequenced, and two biological replicates were sequenced as a control against which changes of gene expression were ascertained.