Planta

, Volume 227, Issue 1, pp 143–150

Potato steroidal glycoalkaloid levels and the expression of key isoprenoid metabolic genes

Original Article

DOI: 10.1007/s00425-007-0602-3

Cite this article as:
Krits, P., Fogelman, E. & Ginzberg, I. Planta (2007) 227: 143. doi:10.1007/s00425-007-0602-3

Abstract

The potato steroidal glycoalkaloids (SGA) are toxic secondary metabolites, and their total content in tubers should not exceed 20 mg/100 g fresh weight. The two major SGA in cultivated potato (Solanum tuberosum) are α-chaconine and α-solanine. SGA biosynthetic genes and the genetic factors that control their expression have not yet been determined. In the present study, potato genotypes exhibiting different levels of SGA content showed an association between high SGA levels in their leaves and tubers and high expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase 1 (hmg1) and squalene synthase 1 (pss1), genes of the mevalonic/isoprenoid pathway. Transcripts of other key enzymes of branches of the isoprenoid pathway, vetispiradiene/sesquiterpene synthase (pvs1) and sterol C24-methyltransferase type1 (smt1), were undetectable or exhibited stable expression regardless of SGA content, respectively, suggesting facilitated precursor flow to the SGA biosynthetic branch. The transcript ratio of solanidine glucosyltransferase (sgt2) to solanidine galactosyltransferase (sgt1) was correlated to the documented chaconine-to-solanine ratio in the tested genotypes. Significantly higher expression of hmg1, pss1, smt1, sgt1 and sgt2 was monitored in the tuber phelloderm than in the parenchyma of the tuber’s flesh, targeting the former as the main SGA-producing tissue in the tuber, in agreement with the known high SGA content in the layers directly under the tuber skin.

Keywords

HMGR1 Isoprenoid pathway Potato steroidal glycoalkaloids PSS1 Solanum 

Abbreviations

SGA

Steroidal glycoalkaloids

HMGR

3-Hydroxy-3-methylglutaryl coenzyme A reductase

PSS

Squalene synthase

SMT1

Sterol C24-methyltransferase type1

SGT1

Solanidine galactosyltransferase

SGT2

Solanidine glucosyltransferase

Supplementary material

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Life SciencesBar-Ilan UniversityRamat GanIsrael
  2. 2.Department of Vegetable Research, Institute of Plant SciencesARO, The Volcani CenterBet DaganIsrael

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