Alcázar Rubén, García-Martínez José L, Cuevas Juan C, Tiburcio Antonio F, Altabella Teresa
Laboratori de Fisiologia Vegetal, Facultat de Farmàcia, Universitat de Barcelona, Avda Diagonal, 643. 08028-Barcelona, Spain.
Plant J. 2005 Aug;43(3):425-36. doi: 10.1111/j.1365-313X.2005.02465.x.
We have obtained Arabidopsis thaliana transgenic plants constitutively overexpressing ADC2, one of the two genes encoding arginine decarboxylase (ADC) in Arabidopsis. These plants contained very high levels of putrescine (Put) but no changes were observed in spermidine and spermine contents. The results obtained from quantification of free and conjugated polyamines suggest that conjugation may be a limiting step for control of Put homeostasis within a non-toxic range for plant survival. Transgenic plants with increased levels of ADC2 transcript and elevated Put content showed dwarfism and late-flowering, and the phenotype was rescued by gibberellin A3 (GA3) application. The contents of bioactive GA4 and GA1, and of GA9 (a precursor of GA4), as well as the levels of AtGA20ox1, AtGA3ox1 and AtGA3ox3 transcripts (quantified by real-time PCR) were lower in the ADC2 overexpressor plants than in the wild type. No change in the expression of genes encoding earlier enzymes in the GA biosynthesis pathway was detected by microarray analysis. These results suggest that Put accumulation affects GA metabolism through the repression of biosynthetic steps catalyzed by GA 20-oxidase and GA 3-oxidase.
我们获得了组成型过表达拟南芥精氨酸脱羧酶（ADC）两个编码基因之一ADC2的转基因植物。这些植物含有非常高水平的腐胺（Put），但亚精胺和精胺含量未观察到变化。对游离和结合态多胺的定量结果表明，结合可能是在对植物存活无毒的范围内控制Put稳态的一个限制步骤。ADC2转录本水平增加且Put含量升高的转基因植物表现出矮化和开花延迟，并且通过施用赤霉素A3（GA3）可挽救该表型。在ADC2过表达植物中，生物活性GA4和GA1以及GA9（GA4的前体）的含量，以及AtGA20ox1、AtGA3ox1和AtGA3ox3转录本水平（通过实时PCR定量）均低于野生型。通过微阵列分析未检测到GA生物合成途径中编码早期酶的基因表达有变化。这些结果表明，Put积累通过抑制由GA 20-氧化酶和GA 3-氧化酶催化的生物合成步骤来影响GA代谢。
