Study On The Regulation Of Plant Growth And Development By Arabidopsis Transcription Factor ABI5

ABI5 is a basic leucine zipper transcription factor as a result of the fifth mutant of Arabidopsis of which does not respond to ABA.The phenotype of the abi5 mutant is not obviously changed.In addition,the phenotypic changes of over-expressed ABI5 Arabidopsis are reported inconsistently.There are two transcriptional activation regions in the transcription factor ABI5.Its conserved phosphorylation sites presented inhibition to its transcriptional activity.ABI5-overexpressed plants can not display a clear phenotype because of the absence of activated ABI5.Based on this,we deleted the transcriptional repression regions of ABI5 and constructed an active form of recombinant ABI5 molecules(rABI5s)to understand the effects of ABI5 on plant growth and development when activated.By comparing wild type,over-expressed ABI5 gene and over-expressed ABI5 recombinant gene,we get some results as follows:1.Seed germination ratio of the over-expressed rABI5 plants significantly decreasedThe seed germination ratio of wild-type Arabidopsis and rABI5 transgenic plants was counted after 5-day germination.Germination ratio of wild-type seeds was 82%,the ratio of pMX-1-1 plants was 46%,pMX-2-1 transgenic line was 51%,pMX-3-3line was 40%,and pMX-4-4 lines was 80%.2.Rosettes of the over-expressed rABI5 Arabidopsis plants were longitudinally elongatedThe size of rosette leaves of wild type Arabidopsis seedlings and over-expressed rABI5 was measured.A length of wild type seedling was 26.5 mm and its width was12.5 mm.Rosettes of pMX-1-7 transgenic seedlings were 30 mm long and 13 mm wide.Rosettes of pMX-4-2 transgenic seedlings were 29 mm long and 13 mm wide.Statistical analysis showed that there was a significant difference in the length of rosette leaves between wild-type and over-expressed lines.3.Flowering time is earlier in the over-expressed rABI5 Arabidopsis plantsUnder the same growing conditions,wild-type Arabidopsis plants began to bolt after 30 days.The Arabidopsis lines transformed with pMX-1-1,pMX-3-2 and pMX-4-2 began to bolt after 25-day,26-day,and 27-day growth,respectively.The rABI5-over-expressed lines showed early flowering phenotypes.4.Drought resistance of the over-expressed rABI5 Arabidopsis plants was significantly enhanced.After three weeks of growth,wild-type Arabidopsis seedlings and all rABI5-over-expressed lines were stopped watering for 10 days.Leaves of wild-type seedlings were dry,but leaves of the over-expressed lines were green in spite of wilt.After one-week rehydration,leaves of wild-type seedlings were dry and dead.However,leaves of over-expressed lines returned lively green and plants can grow to flowering stage.