Expression Of Chalcone Isomerase Research Articles

Spatial patterns of expression of flavonoid/isoflavonoid pathway genes during interactions between roots of Medicago truncatula and the mycorrhizal fungus Glomus versiforme

SummaryA combination of Northern blot analysis and in situ hybridization was used to measure and localize changes in the levels of transcripts encoding five enzymes of phenylpropanoid/flavonoid/isoflavonoid metabolism in Medicago truncatula roots following colonization with the mycorrhizal fungus Glomus versiforme. In colonized roots, elevated levels of phenylalanine ammonia‐lyase (PAL) and chalcone synthase (CHS) transcripts were detected specifically in the cortical cells containing arbuscules. This localization was discrete, and elevated levels of transcripts were not observed in adjacent, non‐colonized cells. In contrast, isoflavone reductase (IFR) transcripts, which were detected at relatively high levels in the cortical cells of non‐colonized roots, were almost undetectable in the colonized cortical cells containing arbuscules and were also lowered in adjacent cells. The expression of chalcone isomerase (CHI) and isoliquiritigenin 2′‐O‐methyltransferase (ChalOMT) was unaffected by colonization, and the tissue‐specific patterns of gene expression were the same as in non‐colonized roots. It is concluded that the establishment of the mycorrhizal interaction results in cell type‐specific differential expression of genes of phenylpropanoid/flavonoid/isoflavonoid biosynthesis, which may be causally related to arbuscule development.

Chalcone isomerase in flowers of mutants of Petunia hybrida

The effect of the gene Po on the activity of chalcone isomerase was investigated in Petunia hybrida. Furthermore, isomerase activities isolated from petals were compared with those extracted from anthers. No effect of Po on the pH-dependence of the isomerase and its kinetic properties was observed. With respect to these criteria, the enzyme extracted from anthers behaved in an identical manner to that extracted from petals. Upon chromatofocussing of a petal extract two peaks of activity were present with slightly different isoelectric points (pI 4.8 and pI 5.1). The occurrence of these activities was dependent on the method of enzyme extraction. An isolation procedure using polyvinylpyrrolidone besides Dowex to remove phenolic compounds, followed by (NH4)2SO4 precipitation of the protein, resulted in only one peak of isomerase at a pI of 5.3. This observation was independent of Po and did not occur in anthers. In anthers one peak of enzyme activity with a pI of 4.5 was present. The moleuclar weight of the isomerase from flowers (62,500 dalton in Po-dominant and Po-recessive plants) differed from the molecular weight of the anther enzyme (44,000 dalton). In Po-recessive mutants the isomerase activity in mature flowers was low compared with Po-dominant mutants, indicating that the mutation in Po either reflects a temporal mutation in the expression of chalcone isomerase or an increased degradation of the enzyme.