What are the structural and functional differences between HMGR1 and HMGR2 of tomatoes?

Answer 1

Both these enzymes are involved in the production of mevalonic acid.

HMGR1 is involved with growth processes requiring phytosterol production.

HMG1 is highly expressed during the early stages of fruit development, when sterol biosynthesis is required for membrane biogenesis during cell division and expansion. HMG2 expression is not detectable in young fruit, but is activated during fruit maturation and increases strongly during ripening, in parallel with the accumulation of lycopene.

You can search the EMBL site to compare genes.

Answer 2

Regulation of isoprenoid end-product synthesis required for normal growth and development in plants is not well understood. To investigate the extent to which specific genes for the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) are involved in end-product regulation, we manipulated expression of the HMG1 and HMG2 genes in tomato (Lycopersicon esculentum) fruit using arachidonic acid (AA). In developing young fruit AA blocked fruit growth, inhibited HMG1, and activated HMG2 expression. These results are consistent with other reports indicating that HMG1 expression is closely correlated with growth processes requiring phytosterol production. In mature-green fruit AA strongly induced the expression of HMG2, PSY1 (the gene for phytoene synthase), and lycopene accumulation before the normal onset of carotenoid synthesis and ripening. The induction of lycopene synthesis was not blocked by inhibition of HMGR activity using mevinolin, suggesting that cytoplasmic HMGR is not required for carotenoid synthesis. Our results are consistent with the function of an alternative plastid isoprenoid pathway (the Rohmer pathway) that appears to direct the production of carotenoids during tomato fruit ripening.

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Answer 3

donr

Answer 4

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