Developmental regulation of the gibberellin biosynthetic gene GA1 in Arabidopsis thaliana

Abstract

SummaryThe GA 1 gene of Arabidopsis thaliana encodes ent.kaurene synthase A (KSA), which catalyzes the first committed step in the biosynthetic pathway of the plant hormone gibberellin (GA). Its location in the GA biosynthetic pathway has led to speculation that KSA regulation is one of the controlling steps. However, because KSA activity is so low that it is only measurable in Arabidopsis siliques, GA1 promoter-GUS reporter gene fusions and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) were used to examine the expression pattern of GAl. The results from this study indicate that GA 1 gene expression is highly regulated during growth and development, and it is restricted to specific cell types at the sites of expression. GA1 promoter activity is highest in rapidly growing tissues, e.g. shoot apices, root tips, developing flowers and seeds. It is also active in the vascular tissue of some non-growing organs, such as expanded leaves, suggesting that these leaves may be a site of GA synthesis for transport to other organs. It was also found that the first one or two introns in the GA1 gene are required for proper expression. Because of the high degree of regulation, GA1 may act as a gatekeeper, controlling the flow of metabolites into the GA biosynthetic pathway, while the levels of specific bioactive GAs are controlled by other downstream steps.

AtGA3ox2, a Key Gene Responsible for Bioactive Gibberellin Biosynthesis, Is Regulated during Embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis

“…Transgenic reporter lines that carry the GUS gene under control of AtCPS or AtGA20ox1 cis-regulatory elements were crossed to lec2-1 and fus3-8 mutants. AtCPS (GA1 gene) is expressed mainly in the provasculature of the wild-type embryo, as shown on Figure 3A (Silverstone et al, 1997;Yamaguchi et al, 2001). A GUS staining pattern similar to wild type was observed in all mutants and wild type (Fig.…”

“…We analyzed the expression levels of 12 GA-biosynthetic genes in siliques of wildtype, lec2-1, and fus3-8 mutants using real-time RT-PCR (see ''Materials and Methods'' for a complete list). The majority of these genes displayed no significant modification of their transcript level, as shown for AtCPS, AtGA20ox1, and AtGA3ox1, three genes playing a role in major biosynthesis steps and whose developmental regulations are well known (Silverstone et al, 1997;Meier et al, 2001;Yamaguchi et al, 2001;Fig. 2B).…”

Epigenetic Control of a Transcription Factor at the Cross Section of Two Antagonistic Pathways

“…b-glucuronidase (GUS) activity was assessed after infiltrated leaves were histochemically stained for 24 h with 5-bromo-4chloro-3-indolyl (X-gluc) as a substrate. 26 Seeds from Arabidopsis Col 0 wild type and from Col 0 wild type and from the atx1-mutant line were grown at 24˚C under 14 hr light/10 hr darkness. The atx1 mutant line carried a Ti-insertion deleting the PHD-SET domains.…”

TheGibberellic Acid Stimulated-LikeGene Family in Maize and Its Role in Lateral Root Development

“…This pathway could also be active in lateral roots (Hardtke, 2003). GA1, which catalyzes the first step in GA 3 biosynthesis, is highly expressed in lateral root meristems (Silverstone et al, 1997), which could suggest a role of ZmGSL1b, ZmGSL2, ZmGSL4, ZmGSL6, and ZmGSL9 in GA 3 -dependant lateral root formation. Remarkably, splice variant ZmGSL1b, which is associated with expression in the pericycle and thus lateral root formation, is very strongly induced by GA 3 , while ZmGSL1a transcript abundance is only slightly increased by GA 3 in parenchyma cells.…”