Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, RD 10, Versailles, France.
Ann Bot. 2011 May;107(6):1017-27. doi: 10.1093/aob/mcr039. Epub 2011 Mar 1.
Reproductive phase change in Arabidopsis thaliana is characterized by two transitions in phytomer identity, the differentiation of the first elongate internode (bolting transition) and of the first flower (floral transition). An evaluation of the dynamics of these transitions was sought by examining the precision of the corresponding phytomer identity changes.
The length of the first elongate internode and the frequency of chimeric inflorescence structures, e.g. paraclades not subtended by a leaf (no-leaf/paraclades) and flowers subtended by a bract (bract/flowers), were measured in the Wassilewskija (Ws) accession and 47 early flowering mutants under a wide range of photoperiods. The impact of photoperiodic perturbations applied to Ws plants at different times of development was also evaluated.
In Ws, both types of characters were remarkably constant across photoperiods in spite of a high degree of interindividual variability. Bract/flowers were not normally produced in Ws, but they were observed in conditions that suggest enhanced light signalling, e.g. in response to continuous light perturbations and in mutants with reduced hypocotyl elongation. In contrast, no-leaf/paraclades were normally present in approx. 20 % of Ws plants, and their frequency was increased in conditions that suggest reduced light signalling, e.g. in mutants with altered specification of long-day responses. The length of the first elongate internode was unrelated to the rate of stem elongation and to the regulation of reproductive phase change.
Bract/flowers and no-leaf/paraclades corresponded to opposite effects on the floral transition that reflected different dynamics of progression to flowering. In contrast, the length of the first elongate internode was only indirectly related to the regulation of reproductive phase change and was mainly dependent on global morphogenetic constraints. This paper proposes that morphogenetic variability could be used to identify critical phases of development and characterize the canalization of developmental patterns.
拟南芥的生殖阶段变化的特征在于两个生殖节间身份的转变，即第一个伸长节间的分化（抽薹转变）和第一个花的分化（花转变）。通过检查相应的生殖节间身份变化的精度，寻求对这些转变的动态进行评估。
在广泛的光周期范围内，测量 Wassilewskija（Ws）品系和 47 个早期开花突变体中的第一个伸长节间的长度和嵌合体花序结构的频率，例如没有叶子支撑的副穗（无叶/副穗）和有苞片支撑的花（苞片/花）。还评估了在不同发育时间向 Ws 植物施加光周期干扰的影响。
在 Ws 中，尽管个体间变异性很大，但两种类型的特征在光周期之间都非常稳定。正常情况下，Ws 中不产生苞片/花，但在增强光信号的条件下观察到它们，例如在连续光干扰下和在减少下胚轴伸长的突变体中。相反，无叶/副穗在大约 20%的 Ws 植物中正常存在，并且在暗示光信号减少的条件下，其频率增加，例如在改变长日反应的规范的突变体中。第一个伸长节间的长度与茎伸长的速度和生殖阶段变化的调节无关。
苞片/花和无叶/副穗对应于对花转变的相反影响，反映了向花转变的不同动态。相比之下，第一个伸长节间的长度仅与生殖阶段变化的调节间接相关，主要取决于全局形态发生约束。本文提出，形态发生变异性可用于识别发育关键阶段并表征发育模式的渠道化。
