Methylation of gibberellins by Arabidopsis GAMT1 and GAMT2

Marina Varbanova, Shinjiro Yamaguchi, Yue Yang, Katherine McKelvey, Atsushi Hanada, Roy Borochov, Fel Yu, Yusuke Jikumaru, Jeannine Rosa, Diego Cortea, Je Ma Choong, Joseph P. Noel, Lew Mander, Vladimir Shulaev, Yuji Kamiya, Steve Rodermel, David Weiss, Eran Picharsky*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

221 Scopus citations


Arabidopsis thaliana GAMT1 and GAMT2 encode enzymes that catalyze formation of the methyl esters of gibberellins (GAs). Ectopic expression of GAMT1 or GAMT2 in Arabidopsis, tobacco (Nicotiana tabacum), and petunia (Petunia hybrida) resulted in plants with GA deficiency and typical GA deficiency phenotypes, such as dwarfism and reduced fertility. GAMT1 and GAMT2 are both expressed mainly in whole siliques (including seeds), with peak transcript levels from the middle until the end of silique development. Within whole siliques, GAMT2 was previously shown to be expressed mostly in developing seeds, and we show here that GAMT1 expression is also localized mostly to seed, suggesting a role in seed development. Siliques of null single GAMT1 and GAMT2 mutants accumulated high levels of various GAs, with particularly high levels of GA1 in the double mutant. Methyleted GAs were not detected in wild-type siliques, suggesting that methylation of GAs by GAMT1 and GAMT2 serves to deactivate GAs and initiate their degradation as the seeds mature. Seeds of homozygous GAMT1 and GAMT2 null mutants showed reduced inhibition of germination, compared with the wild type, when placed on plates containing the GA biosynthesis inhibitor ancymidol, with the double mutant showing the least inhibition. These results suggest that the mature mutant seeds contained higher levels of active GAs than wild-type seeds.

Original languageAmerican English
Pages (from-to)32-45
Number of pages14
JournalPlant Cell
Issue number1
StatePublished - Jan 2007


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