三色苋(Amaranthus tricolor)不同器官中的甜菜碱(GB)含量显著不同.除子叶外,根、茎和叶的GB含量和茎、叶中的胆碱单加氧酶(CMO)含量都因300 mmol/L的NaCl处理而增加.甜菜碱醛脱氢酶(BADH)的表达无论盐处理与否在所有器官中都能检测到,其含量变化不大.当种子发芽时,具备合成GB的能力,CMO含量增加;在此之前未能检测到CMO,也不能合成GB.研究结果表明三色苋响应盐胁迫而合成GB的关键酶是CMO.%The glycine betaine (GB) and related enzymes contents, i.e., choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH), of seeds, roots, stems, cotyledons, leaves, and flowers in Amaranthus tricolor under salt stress were determined. GB content varied significantly among different organs. GB content in the leaves was higher at the beginning of unfolding stage and decreased during maturation and senescence. GB content in the roots was very low through the life of plant. GB content in the roots, stems, leaves and flowers increased by exposure to NaC1 300 mmol/L, except in the cotyledon where it was low and remained unchanged under salt stress. Induction of GB increase by salt stress was greater in mature and old leaves than in younger leaves.CMO protein content was low in the all organs, but that in stems and leaves was significantly increased by the addition of NaC1 300 mmol/L, and was concomitant with the accumulation of GB in their tissues. BADH protein was detected in all organs. But, the levels of BADH protein did not always vary among different organs as a result of salt stress. The effect of salt stress on BADH protein content was small and in consistent in mature and old leaves. Seeds after being soaked in water for 24 h were unable to synthesize GB. When the seeds started to germinate after being in water for 48 h, they showed an ability to synthesize GB under salt stress. This was accompanied with an increase in their CMO protein content, whereas their BADH protein level did not change. The present re sults indicate that CMO protein is important to GB synthesis when A. tricolor is under salt stress.
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