Glycolytic gene expression in amphibious Acorus calamus L. under natural conditions

Acorus calamus L is an amphibious plant, which is exposed to periods of flooding and consequently hypoxic conditions as a part of its natural life cycle. Previous experiments under laboratory conditions have shown that the plant can survive for two months in the complete absence of oxygen, and that during this period the expression of genes encoding the glycolytic enzymes fructose-1,6-bisphosphate aldolase (ALD), pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) is induced in leaves and rhizomes (Bucher and Kuhlemeier, 1993). Here we studied the expression of ALD and ADH through two years in the natural habitat of A. calamus. Under natural conditions roots and rhizomes were always submerged but newly grown leaves emerged in spring; in autumn the leaves senesced and the whole plant was submerged again. High Ald and Adh mRNA levels in leaf and rhizome were found only in winter when the leaves were entirely submerged. Upon leaf emergence in spring the mRNA levels rapidly declined. Under controlled experimental conditions expression of Ald and Adh was not induced by low temperature. The combination of laboratory and field experiments supports the hypothesis that oxygen deprivation rather than low temperature is a major regulator of glycolytic gene expression in A. calamus. The possible role of other environmental factors is also discussed.Abbreviations ADH alcohol dehydrogenase - Adh gene encoding ADH - ALD cytoplasmic fructose-1,6-bisphosphate aldolase - Ald gene encoding ALD - PDC pyruvate decarboxylase - Pdc gene encoding PDC