Higher plant calreticulins have acquired specialized functions in Arabidopsis.
Higher plant calreticulins have acquired specialized functions in Arabidopsis.
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DOI：
10.1371/journal.pone.0011342
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发表时间：
2010-06-28
期刊：
影响因子：
3.7
通讯作者：
Persson S
中科院分区：
文献类型：
--
作者：
Christensen A;Svensson K;Thelin L;Zhang W;Tintor N;Prins D;Funke N;Michalak M;Schulze-Lefert P;Saijo Y;Sommarin M;Widell S;Persson S
钙网蛋白（Calreticulin， CRT）是一种普遍存在于动物体内的内质网蛋白，参与蛋白质折叠和钙稳态等多种细胞过程。与动物一样，植物也进化出了不同的crt，但它们的生理功能却鲜为人知。拟南芥含有三种CRT蛋白，其中两个CRT AtCRT1a和CRT1b代表一个亚群，而AtCRT3是一个不同的成员。通过在缺乏CRT的小鼠成纤维细胞中表达单个拟南芥家族成员，我们发现两个亚群都保留了基本的CRT功能，包括ER Ca2+保持电位和假定的伴侣能力。然而，由于在成纤维细胞中缺乏CRT而导致的其他更普遍的细胞缺陷，如细胞粘附缺陷，并没有完全恢复。此外，在植物表达、蛋白定位和突变分析中显示，这三种拟南芥crt获得了特殊的功能。AtCRT1a和CRT1b家族成员似乎是一般ER伴侣网络的组成部分。相反，正如最近所显示的，AtCRT3与免疫应答相关，并且对细菌病原体相关分子模式（PAMP） elf18的应答至关重要，该模式源于延伸因子(EF)-Tu。而组成型表达的AtCRT1a完全补充了Atcrt1b突变体，而AtCRT3则没有。我们得出结论，拟南芥中两个CRT亚群的生理功能已经分化，导致AtCRT3在PAMP相关反应中发挥作用，并且AtCRT1a和CRT1b可能具有更普遍的伴侣功能。
Calreticulin (CRT) is a ubiquitous ER protein involved in multiple cellular processes in animals, such as protein folding and calcium homeostasis. Like in animals, plants have evolved divergent CRTs, but their physiological functions are less understood. Arabidopsis contains three CRT proteins, where the two CRTs AtCRT1a and CRT1b represent one subgroup, and AtCRT3 a divergent member. Through expression of single Arabidopsis family members in CRT-deficient mouse fibroblasts we show that both subgroups have retained basic CRT functions, including ER Ca2+-holding potential and putative chaperone capabilities. However, other more general cellular defects due to the absence of CRT in the fibroblasts, such as cell adhesion deficiencies, were not fully restored. Furthermore, in planta expression, protein localization and mutant analyses revealed that the three Arabidopsis CRTs have acquired specialized functions. The AtCRT1a and CRT1b family members appear to be components of a general ER chaperone network. In contrast, and as recently shown, AtCRT3 is associated with immune responses, and is essential for responsiveness to the bacterial Pathogen-Associated Molecular Pattern (PAMP) elf18, derived from elongation factor (EF)-Tu. Whereas constitutively expressed AtCRT1a fully complemented Atcrt1b mutants, AtCRT3 did not. We conclude that the physiological functions of the two CRT subgroups in Arabidopsis have diverged, resulting in a role for AtCRT3 in PAMP associated responses, and possibly more general chaperone functions for AtCRT1a and CRT1b.
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