Starch degradation by alpha-amylase in tobacco leaves during the curing process

Naoto Yamaguchi, Shoichi Suzuki, Amane Makino

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Tobacco (Nicotiana tabacum L.) leaf starch is degraded to sugars through curing (42°C/82.3% relative humidity/72 h). Total carbohydrate content remained almost constant, starch content decreased markedly, and soluble sugar content (mostly glucose) increased. α-Amylase and starch phosphorylase activities increased sixfold and threefold, respectively, whereas β-amylase activity was unaltered and isoamylase activity decreased. Increased α-amylase activity was accompanied by increased α-amylase protein levels. Although tobacco has four α-amylase gene members, only NtAMY1 mRNA levels increased. For other starch degradation genes, such as NtBAM1 and NtBMY2 (β-amylase), NtISO1 and NtISO2 (isoamylase) and NtGWD1 and NtGWD3 (glucan water dikinase), the mRNA levels remained unaltered during the first 48 h of curing. NtAMY1 expression was induced by osmotic stress but was unaffected by high temperature and/or injury stresses. Similarly, soluble sugar contents were largely increased by osmotic stress. This suggests that starch is degraded by α-amylase during curing and that α-amylase is coded by NtAMY1, induced by osmotic stress.

Original languageEnglish
Pages (from-to)904-911
Number of pages8
JournalSoil Science and Plant Nutrition
Volume59
Issue number6
DOIs
Publication statusPublished - 2013

Keywords

  • curing process
  • osmotic stress
  • starch degradation
  • tobacco leaf
  • α-amylase

ASJC Scopus subject areas

  • Soil Science
  • Plant Science

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