Characterization of a potato cDNA encoding an Aux/IAA protein regulated by stress.

ZANETTI ME; TERRILE MC; ARCE D; GODOY AV; CASALONGUÉ C

USA

Congreso; Annual Meeting of Plant Biology; 2002

ASPB

Indol-3-acetic acid (IAA) plays an important role in an extent range of growth and development processes. It has been reported that Aux/IAA genes are rapidly induced by exogenous treatment with auxin. Their nuclear localization and resemblance to prokaryotic DNA binding domain led to the suggestion that Aux/IAA proteins could function as transcription factors. We report the identification and characterization of a potato cDNA encoding an Aux/IAA protein named StIAA. StIAA was isolated by differential screening of a 24 h Fusarium eumartii infected potato tuber using PCR-amplified subtracted and control probes. StIAA cDNA was 1680 bp long, comprising 291 bp 5' untraslated region, an open reading frame of 1050 bp and 338 bp 3' uncoding region. It encodes a 37,4 kDa protein with a theoretical isoelectric point of 7.1. Comparison of the predicted amino acid sequence of StIAA with Gen Bank and EMBL databases revealed a high degree of conservation with others Aux/IAA proteins. The highest identity (88%) was found with the sequence of Nicotiana tabacum IAA9. The low number of hybridizing fragment detected by genomic Southern blot suggests that StIAA may be present as a single copy in the potato genome. A single transcript of approximately 1.8 kb was detected in potato leaves after exogenous application of auxin. The StIAA transcript level similarly increased in potato tubers in response to wounding and Fusarium eumartii infection at 4 and 8 h after initial treatment. At 12, 16 y 24 h after inoculation with F. eumartii, the StIAA transcript level was two fold higher than in wound tubers. The implications of these findings for a potential involvement of Aux/IAA genes in the potato defense response against biotic stress are still unknown.