Meins F, Wenzler H
Symp Soc Exp Biol. 1986;40:155-70.
During development parts of plants become determined for specific fates which can persist in populations of dividing cells. Students of plant development have tended to favour the view that the determined state is stabilized at the supracellular level. We provide evidence for the alternative view that determination can be inherited at the cellular level. This conclusion is based on the observation that cultured cells derived from the leaf lamina and cortex of the stem of tobacco plants inherit different states of cytokinin requirement. Plant regeneration experiments show that the cytokinin-requiring (C-) state characteristic of leaf cells and the cytokinin autotrophic (C+) state characteristic of cortex cells are stable but not permanent. Progeny of both cell types can give rise to complete plants with tissues exhibiting the cytokinin requirement of comparable tissues of seed grown plants. Pith cells can shift from the C- to the C+ state by a process known as habituation. Evidence is presented that this epigenetic change is stabilized by a positive-feedback mechanism in which cytokinins appear to promote their own biosynthesis. A single dominant, Mendelian gene, H1-2, controls expression of the C- and C+ phenotypes. There are hints that this gene changes state in cultured cells at rates expected for epigenetic modifications. This suggests that the C- and C+ state can also be stabilized by genetic mechanisms.
在植物发育过程中，植物的某些部分会被确定为特定的命运，这些命运可以在分裂细胞群体中持续存在。植物发育领域的学者倾向于支持这样一种观点，即确定状态在超细胞水平上得以稳定。我们为另一种观点提供了证据，即确定状态可以在细胞水平上遗传。这一结论基于以下观察结果：从烟草植株的叶片和茎皮层衍生而来的培养细胞继承了不同的细胞分裂素需求状态。植物再生实验表明，叶片细胞特有的细胞分裂素需求（C-）状态和皮层细胞特有的细胞分裂素自养（C+）状态是稳定的，但并非永久性的。这两种细胞类型的后代都能发育成完整植株，其组织表现出与种子生长植株相应组织类似的细胞分裂素需求。髓细胞可以通过一种称为适应的过程从C-状态转变为C+状态。有证据表明，这种表观遗传变化通过一种正反馈机制得以稳定，在该机制中细胞分裂素似乎促进自身的生物合成。一个单一的显性孟德尔基因H1-2控制C-和C+表型的表达。有迹象表明，该基因在培养细胞中的状态变化速率符合表观遗传修饰的预期。这表明C-和C+状态也可以通过遗传机制得以稳定。
