Functional domains of SPATULA, a bHLH transcription factor involved in carpel and fruit development in Arabidopsis
Functional domains of SPATULA, a bHLH transcription factor involved in carpel and fruit development in Arabidopsis
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DOI：
10.1111/j.1365-313x.2008.03469.x
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发表时间：
2008-07-01
期刊：
影响因子：
7.2
通讯作者：
Smyth, David R.
中科院分区：
文献类型：
--
作者：
Groszmann, Michael;Paicu, Teodora;Smyth, David R.
SPATULA （SPT）基因参与产生中隔、花柱和柱头：由心皮边缘产生的特殊组织。通过在物种数据库中匹配AtSPT扩展bHLH区域内的序列，在植物、水稻和裸子植物中鉴定出12个同源物。除了bHLH区域外，还发现了两个保守结构域：一个两亲螺旋结构域和一个酸性结构域。这些基因在番茄同源基因中是保守的，这可以恢复拟南芥spt突变体的心皮功能。酸性结构域是SPT心皮功能所必需的，而两亲性螺旋支持它。核定位需要重叠bHLH结构域的二部序列，bHLH C端附近的保守β链发生突变会导致SPT功能丧失。SPT显然是一种转录激活剂，SRDX抑制结构域的加入使SPT突变体的表型发生变化。人工激活35S:SPT-VP16构建体的表达可以诱导萼片的桃核特性，并在雌蕊中产生新的缺陷。这些破坏与STYLISH2基因的异位表达有关，尽管STYLISH2的表达不需要SPT功能。未修饰的SPT的异位表达不会引起这种变化，这意味着SPT与仅存在于SPT正常活跃区域的必需共激活因子相关。由于VP16激活域可以在一定程度上弥补两亲螺旋结构域和酸性结构域的缺失，这些结构域通常可以与这些共激活剂相互作用。
The SPATULA (SPT) gene is involved in generating the septum, style and stigma: specialized tissues that arise from carpel margins. By matching sequences within the extended bHLH region of AtSPT across species databases, twelve orthologues were identified in eudicots, rice and a gymnosperm. Two conserved structural domains were revealed in addition to the bHLH region: an amphipathic helix and an acidic domain. These are conserved in the tomato orthologue, which can restore carpel function to spt mutants of Arabidopsis. The acidic domain is essential for SPT carpel function, and the amphipathic helix supports it. A bipartite sequence overlapping the bHLH domain is required for nuclear localization, and a mutation in the conserved beta strand adjacent to the bHLH C terminus results in the loss of SPT function. SPT apparently acts as a transcriptional activator, as the addition of the SRDX repression domain phenocopies the spt mutant phenotype. Expression of an artificially activating 35S:SPT-VP16 construct can induce carpelloid properties in sepals, and new defects in the gynoecium. These disruptions are associated with ectopic expression of the STYLISH2 gene, although STYLISH2 expression does not require SPT function. Ectopic expression of unmodified SPT does not induce such changes, implying that SPT acts in association with essential coactivators present only in regions where SPT is normally active. Because the VP16 activation domain can compensate to some extent for the loss of the amphipathic helix and acidic domain, these domains may normally interact with such co-activators.