Garcês Helena M P, Champagne Connie E M, Townsley Brad T, Park Soomin, Malhó Rui, Pedroso Maria C, Harada John J, Sinha Neelima R
Section of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15578-83. doi: 10.1073/pnas.0704105104. Epub 2007 Sep 24.
Plant somatic cells have the remarkable ability to regenerate an entire organism. Many species in the genus Kalanchoë, known as "mother of thousands," develop plantlets on the leaf margins. Using key regulators of organogenesis (STM) and embryogenesis (LEC1 and FUS3) processes, we analyzed asexual reproduction in Kalanchoë leaves. Suppression of STM abolished the ability to make plantlets. Here, we report that constitutive plantlet-forming species, like Kalanchoë daigremontiana, form plantlets by coopting both organogenesis and embryogenesis programs into leaves. These species have a defective LEC1 gene and produce nonviable seed, whereas species that produce plantlets only upon stress induction have an intact LEC1 gene and produce viable seed. The latter species are basal in the genus, suggesting that induced-plantlet formation and seed viability are ancestral traits. We provide evidence that asexual reproduction likely initiated as a process of organogenesis and then recruited an embryogenesis program into the leaves in response to loss of sexual reproduction within this genus.
植物体细胞具有再生出完整生物体的非凡能力。许多被称为“千子万孙草”的伽蓝菜属物种在叶缘上长出小植株。利用器官发生（STM）和胚胎发生（LEC1和FUS3）过程的关键调控因子，我们分析了伽蓝菜叶片中的无性繁殖。抑制STM消除了形成小植株的能力。在此，我们报告，像落地生根这样的组成型小植株形成物种，通过将器官发生和胚胎发生程序纳入叶片中来形成小植株。这些物种的LEC1基因存在缺陷，产生无活力的种子，而仅在胁迫诱导下产生小植株的物种具有完整的LEC1基因并产生有活力的种子。后一类物种在该属中处于基部位置，这表明诱导小植株形成和种子活力是祖先性状。我们提供的证据表明，无性繁殖可能最初是作为一种器官发生过程开始的，然后为了应对该属内有性繁殖的丧失，将胚胎发生程序纳入叶片中。
