Reverse genetic characterization of two paralogous acetoacetyl CoA thiolase genes in Arabidopsis reveals their importance in plant growth and development

TitleReverse genetic characterization of two paralogous acetoacetyl CoA thiolase genes in Arabidopsis reveals their importance in plant growth and development
Publication TypeJournal Article
Year of Publication2012
AuthorsJin HN, Song ZH, Nikolau BJ
Journal TitlePlant Journal
Volume70
Pages1015-1032
Date Published06
Type of ArticleArticle
ISBN Number0960-7412
Accession NumberWOS:000305120400010
Keywordsacetoacetyl CoA thiolases, Arabidopsis thaliana, atp-citrate, brassinosteroid biosynthesis, coenzyme-a reductase, embryo lethality, isopentenyl diphosphate isomerases, isoprenoid biosynthesis, lipid bodies, lyase, messenger-rna, mevalonate pathway, phylogenetic analysis, phytosterol, pleiotropic phenotypes, pollen grains, synthase genes
Abstract

Acetoacetyl CoA thiolase (AACT, EC 2.3.1.9) catalyzes the condensation of two acetyl CoA molecules to form acetoacetyl CoA. Two AACT-encoding genes, At5g47720 (AACT1) and At5g48230 (AACT2), were functionally identified in the Arabidopsis genome by direct enzymological assays and functional expression in yeast. Promoter::GUS fusion experiments indicated that AACT1 is primarily expressed in the vascular system and AACT2 is highly expressed in root tips, young leaves, top stems and anthers. Characterization of T-DNA insertion mutant alleles at each AACT locus established that AACT2 function is required for embryogenesis and for normal male gamete transmission. In contrast, plants lacking AACT1 function are completely viable and show no apparent growth phenotypes, indicating that AACT1 is functionally redundant with respect to AACT2 function. RNAi lines that express reduced levels of AACT2 show pleiotropic phenotypes, including reduced apical dominance, elongated life span and flowering duration, sterility, dwarfing, reduced seed yield and shorter root length. Microscopic analysis reveals that the reduced stature is caused by a reduction in cell size and fewer cells, and male sterility is caused by loss of the pollen coat and premature degeneration of the tapetal cells. Biochemical analyses established that the roots of AACT2 RNAi plants show quantitative and qualitative alterations in phytosterol profiles. These phenotypes and biochemical alterations are reversed when AACT2 RNAi plants are grown in the presence of mevalonate, which is consistent with the role of AACT2 in generating the bulk of the acetoacetyl CoA precursor required for the cytosol-localized, mevalonate-derived isoprenoid biosynthetic pathway.

URL<Go to ISI>://WOS:000305120400010http://onlinelibrary.wiley.com/store/10.1111/j.1365-313X.2012.04942.x/asset/j.1365-313X.2012.04942.x.pdf?v=1&t=h4q03kuc&s=cd00ce65f6247e41d6e74b1116205b4e2ca7d179
DOI10.1111/j.1365-313X.2012.04942.x
Alternate JournalPlant J.