Unravelling the molecular basis of functional specialization amongst Arabidopsis thaliana poly(A) polymerase isoforms

在植物和动物中，器官生长到特征大小和形状取决于它们的身份，然而身份程序如何调节原基的生长模式以产生这些特定的大小和形状仍然知之甚少。我们已经在拟南芥中分离出一种突变，这种突变会减少叶子的大小，但增加花器官的大小；这种相反的效果取决于器官的身份，而不是器官在茎上的位置。该突变代表PAP1的氨基酸交换，PAP1是三种典型的核多聚(A)聚合酶之一，负责聚合腺苷化前体信使rna （pre- mrna）。虽然PAP1功能的完全丧失似乎是致命的，但两种密切相关的其他核多聚(A)-聚合酶（PAP2, PAP4）的突变在孤立情况下不会显示出表型。因此，我们提出不同的PAP亚型处理细胞前mrna的特定亚群，并且pap1依赖性亚群包含编码生长调节因子的器官特异性转录物。因此，本提案的主要目的是：(1)使用全基因组方法确定叶片和花中pap1依赖转录本的集合；(2)了解编码蛋白如何促进pap1突变体相反的生长表型；(3)了解生长表型身份依赖的基础；(4)研究PAP2和PAP4的功能及其优先处理的转录本子集；(5)确定不同PAP亚型之间功能专门化的分子基础。

In plants and animals, organs grow to characteristic sizes and shapes that depend on their identity, yet how the identity programme modulates growth patterns in primordia to generate these specific sizes and shapes remains poorly understood. We have isolated a mutation in Arabidopsis thaliana that reduces the size of leaves, but increases the size of floral organs; this opposite effect depends on the identity, not the position of the organ on the shoot. The mutation represents an amino-acid exchange in PAP1, one of the three canonical nuclear poly(A)-polymerases responsible for polyadenylating precursor messenger RNAs (pre-mRNAs). While full loss of PAP1 function appears to be lethal, mutations in the two closely related other nuclear poly(A)-polymerases (PAP2, PAP4) do not show a phenotype in isolation. We therefore propose that the different PAP isoforms process specific subsets of cellular pre-mRNAs and that the PAP1-dependent subset contains organ-specific transcripts encoding regulators of growth. Thus, the main aims of this proposal are (1) to determine the set of PAP1-dependent transcripts in leaves and flowers using a genome-wide approach; (2) to understand how the encoded proteins contribute to the opposite growth phenotypes of the pap1 mutant; (3) to understand the basis for the identity-dependence of the growth phenotype; (4) to characterize the functions of PAP2 and PAP4, and the subset of transcripts they preferentially process; and (5) to determine the molecular basis for the functional specialization between the different PAP isoforms.