Emery RJ, Leport L, Barton JE, Turner NC, Atkins CA
Centre for Legumes in Mediterranean Agriculture (R.J.N.E., L.L., C.A. A., J.E.B., N.C.T.).
Plant Physiol. 1998 Aug;117(4):1515-23. doi: 10.1104/pp.117.4.1515.
Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity than corresponding cis-isomers in higher plants. However, this study demonstrates a system within which the predominant CK are cis-isomers. CK were measured at four developmental stages in developing chickpea (Cicer arietinum L. cultivar Kaniva) seeds by gas chromatography-mass spectrometry. Concentrations were highest at an early endospermic fluid stage and fell considerably when the cotyledons expanded. The cis-isomers of zeatin nucleotide ([9R-MP]Z), zeatin riboside ([9R]Z), and zeatin (Z) were present in greater concentrations than those of corresponding trans-isomers: (trans)[9R-MP]Z, (trans)[9R]Z, (trans)Z, or dihydrozeatin riboside. Dihydrozeatin, dihydrozeatin nucleotide, and the isopentenyl-type CK concentrations were either low or not detectable. Root xylem exudates also contained predominantly cis-isomers of [9R-MP]Z and [9R]Z. Identities of (cis)[9R]Z and (cis)Z were confirmed by comparison of ion ratios and retention indices, and a full spectrum was obtained for (cis)[9R]Z. Tissues were extracted under conditions that minimized the possibility of RNase hydrolysis of tRNA following tissue disruption, being a significant source of the cis-CK. Since no isomerization of (trans)[2H]CK internal standards occurred, it is unlikely that the cis-CK resulted from enzymic or nonenzymic isomerization during extraction. Although quantities of total CK varied, similar CK profiles were found among three different chickpea cultivars and between adequately watered and water-stressed plants. Developing chickpea seeds will be a useful system for investigating the activity of cis-CK or determining the origin and metabolism of free CK.
在高等植物中，细胞分裂素（CK）的反式异构体被认为占主导地位，且比相应的顺式异构体具有更强的生物活性。然而，本研究展示了一个以顺式异构体为主导的CK系统。通过气相色谱 - 质谱联用技术，在鹰嘴豆（Cicer arietinum L. 品种Kaniva）种子发育的四个阶段对CK进行了测定。在胚乳早期液体阶段，其浓度最高，而当子叶展开时，浓度大幅下降。玉米素核苷酸（[9R - MP]Z）、玉米素核苷（[9R]Z）和玉米素（Z）的顺式异构体浓度高于相应的反式异构体：（反式）[9R - MP]Z、（反式）[9R]Z、（反式）Z或二氢玉米素核苷。二氢玉米素、二氢玉米素核苷酸和异戊烯基型CK的浓度要么很低，要么无法检测到。根木质部渗出液中也主要含有[9R - MP]Z和[9R]Z的顺式异构体。通过比较离子比率和保留指数，确认了（顺式）[9R]Z和（顺式）Z的身份，并获得了（顺式）[9R]Z的全谱图。在组织破坏后，在尽量减少核糖核酸酶水解tRNA（顺式CK的一个重要来源）可能性的条件下对组织进行提取。由于（反式）[2H]CK内标未发生异构化现象，因此顺式CK不太可能是在提取过程中通过酶促或非酶促异构化产生的。尽管总CK的量有所不同，但在三个不同的鹰嘴豆品种以及充分浇水和水分胁迫的植株之间，发现了相似的CK谱。发育中的鹰嘴豆种子将成为研究顺式CK活性或确定游离CK的来源和代谢的有用系统。
