Non-invasive expressions of ipt in whole plants or roots indicate cytokinins are synthesized in plant aerial parts, and coordinate with light affect on the phenotypes and the formation of anthocyanins,lignins

摘要

To study the plant roots how in response to ipt gene activation, the transcriptional fusions of ipt-GUS and GUS-ipt were expressed in roots, or in whole plants of Arabidopsis under the control of a root-specific promoter TobRT7, or a CaMV35S promoter through pOp/LhG4 system in non-invasive conditions. The transgenic plants with constitutive expression of ipt-GUS or GUS-ipt showed 15-25 fold, or 1-2 fold increased cytokinin levels respectively. ipt-GUS expressing Arabidopsis had severe root inhibition, serrated leaves, no or few sterile flowers, and an enlarged and retard phenotypes. The seedlings of enlarged phenotype had an enlarged shoot and shoot apical meristem. The ratio of the two phenotypes related with sucrose content in medium and light intensity. While, GUS-ipt expressing Arabidopsis grew faster, flowered early, and had more lateral shoots. However, when ipt-GUS and GUS-ipt were specially expressed in roots under the control of TobRT7, neither cytokinin content in roots or shoots, nor phenotypes were altered. In cytokinin over-producing ipt-GUS expressing Arabidopsis, light and aerial parts of plants played an important role for cytokinin synthesis and root inhibition, and ipt gene was vigorously expressed at the shoot apical parts. Meanwhile, calli were induced at the shoot apical parts of some cytokinin over-producing ipt-GUS expressing Arabidopsis. Increased cytokinins in ipt-GUS expressing Arabidopsis induced the syntheses of anthocyanins and lignins, while light speeded up the anthocyanin accumulation. The endogenous increased cytokinins and exogenous addition of sucrose in MS medium caused the similar effects on the formation of anthocyanins and lignins in shoot, especially in shoot apical meristem. Cytokinins induced CHS transcription in ipt-GUS expressing Arabidopsis seedlings in vigorous vegetative growth period, in which the transcription of CHS was low in wild type Columbia.