Differential Gene Expression Signatures of Small Auxin Up-Regulated RNA(SAUR) and Gretchen- Hagen 3 (GH3) 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 storageroot of sweet potato. The present paper reports the expression of auxin responsive functionally distinctcandidate genes such as Small Auxin Up-Regulated RNA (SAUR) and Gretchen-Hagen 3 (GH3) genesregulated by auxin in the storage root of sweet potato. The differential expression of these auxinregulated genes were analyzed in the storage root of sweet potato as compared to non-storage rootusing the Gene Expression Hybridization kit (Part Number 5190-0404; Agilent). During the initial storageroot development of sweet potatoSAURgenes viz.,OsSAUR9, OsSAUR28, OsSAUR29, OsSAUR57wereup-regulatedwhereasOsSAUR17, OsSAUR30, OsSAUR31weredown-regulated. These genes arepresumably involved in auxin synthesis and transport, regulation of cell elongation and cell expansion,root growth, vascular tissue and interaction with cytokinin. TheseSAURgenes may interact with CalCaM-binding protein that acts to transduce second messenger signals into a wide array of cellular signaltransduction responses involving auxin and brassinosteroid.OsGH3.1a probable IAA amido synthasewas moderately up-regulated and presumably involved in the regulation of auxin content, morphologyand growth of storage root in sweet potato. SeveralOsGH3.8,OsGH3.1,OsGH3.3 andOsGH3.11which are probable IAA-amido synthetase were down-regulated. The down-regulation ofGH3.11in thestorage root relates to its interaction with jasmonic acid during storage root formation of sweet potato.