Differential gene expression signatures of auxin response factors and auxin/ indole 3-acetic acid genes in storage root as compared to non-tuber forming fibrous root of sweet potato (Ipomoea batatas)

Abstract

The phytohormone auxin is involved in the cell division, proliferation and initial thickening of storage root of sweet potato. This article reports the differential expression of functionally distinct auxin responsive candidate genes such as Auxin Response Factors (ARF) and Auxin/Indole 3-Acetic Acid (Aux/IAA) in the storage root of sweet potato [Ipomoea batatas (L.) Lam]. The differential expression of ESTs of these auxin regulated genes were analyzed in the storage root of sweet potato as compared to non-storage root using the Gene Expression Hybridization kit (Part Number 5190-0404; Agilent). During the initial storage root development of sweet potato ARF1, ARF2, ARF10, ARF9 and ARF16 are proposed to be involved in regulating genes controlling cell division pattern while ARF7, ARF8 promote cell elongation/expansion and links brassinosteroid, ethylene and auxin and JA interaction, whereas ARF4 is involved in asymmetric pattern establishment. Several Aux/IAA genes, viz. OsIAA2, OsIAA7, OsIAA10, OsIAA21, OsIAA30 were up-regulated whereas, OsIAA4, OsIAA10, OsIAA17, OsIAA21, OsIAA30, OsIAA31 were down-regulated in the storage root as compared to fibrous root of sweet potato. The down-regulation of IAA4 may be significant in determining the storage root length of sweet potato.