Functional divergence of chloroplast Cpn60α subunits during Arabidopsis embryo development.
Functional divergence of chloroplast Cpn60α subunits during Arabidopsis embryo development.
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拟南芥胚胎发育过程中叶绿体Cpn60 α亚基的功能分化
DOI：
10.1371/journal.pgen.1007036
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发表时间：
2017-09
期刊：
影响因子：
4.5
通讯作者：
Zhao J
中科院分区：
文献类型：
--
作者：
Ke X;Zou W;Ren Y;Wang Z;Li J;Wu X;Zhao J
伴侣蛋白是一类分子伴侣，有助于多种底物的折叠和组装。在植物中，叶绿体伴侣蛋白由两种不同类型的亚基Cpn60α和Cpn60β组成，并且Cpn60α和Cpn60β基因的重复在植物中发生的比例很高。然而，人们对多个 Cpn60α 和 Cpn60β 基因在植物中的重要性知之甚少。在这项研究中，我们发现拟南芥编码次要Cpn60α亚基的基因CPNA2（AtCpn60α2）的功能丧失导致球状期胚胎发育停滞，而编码显性Cpn60α亚基的另一个AtCpn60α基因CPNA1（AtCpn60α1）主要影响鱼雷期胚胎子叶的发育。以及此后。进一步的研究表明，CPNA2可以与CPNB2（AtCpn60β2）和CPNB3（AtCpn60β3）形成功能伴侣，而CPNA1的功能伴侣是CPNB1（AtCpn60β1）和CPNB2。我们还发现，含有 CPNA2 的功能性伴侣蛋白可以协助特定底物 KASI（β-酮酰基-[酰基载体蛋白]合酶 I）的折叠，并且由于 CPNA2 功能丧失，KASI 蛋白水平显着降低。此外，KASI 蛋白水平的降低被证明是 cpna2 胚胎停滞的可能原因。我们的研究结果表明，拟南芥中的两个 Cpn60α 亚基在胚胎发育过程中发挥着不同的作用，通过与特定的 AtCpn60β 形成不同的伴侣蛋白来协助特定底物的折叠，从而为植物中 Cpn60α 亚基的功能分歧提供了新的见解。伴侣蛋白是大型寡聚复合物，参与不同物种中众多蛋白质的折叠和组装。与其他类型的伴侣蛋白相比，叶绿体伴侣蛋白的特征是由两种独特类型的亚基 Cpn60α 和 Cpn60β 组成的异源寡聚结构，每种亚基以两种或多种旁系同源形式存在于大多数高等植物中。然而，广泛的亚基类型和复杂的寡聚排列背后的功能意义仍然很大程度上未知。在这里，我们研究了次要 Cpn60α 亚基 AtCpn60α2 在拟南芥胚胎发育中的作用，发现 AtCpn60α2 对于球形胚胎向心形胚胎的转变很重要，而显性 Cpn60α 亚基 AtCpn60α1 的丢失会影响胚胎子叶发育。进一步的研究表明，AtCpn60α2可以与AtCpn60β2和AtCpn60β3形成功能性伴侣蛋白，专门协助底物KASI的折叠，这对于心形胚胎的形成非常重要。我们的研究结果表明，高等植物中Cpn60α基因的重复可以增加叶绿体伴侣底物的潜在数量，并为叶绿体伴侣在植物生长发育中发挥更多作用，从而揭示伴侣蛋白基因的重复与功能特化之间的关系。
Chaperonins are a class of molecular chaperones that assist in the folding and assembly of a wide range of substrates. In plants, chloroplast chaperonins are composed of two different types of subunits, Cpn60α and Cpn60β, and duplication of Cpn60α and Cpn60β genes occurs in a high proportion of plants. However, the importance of multiple Cpn60α and Cpn60β genes in plants is poorly understood. In this study, we found that loss-of-function of CPNA2 (AtCpn60α2), a gene encoding the minor Cpn60α subunit in Arabidopsis thaliana, resulted in arrested embryo development at the globular stage, whereas the other AtCpn60α gene encoding the dominant Cpn60α subunit, CPNA1 (AtCpn60α1), mainly affected embryonic cotyledon development at the torpedo stage and thereafter. Further studies demonstrated that CPNA2 can form a functional chaperonin with CPNB2 (AtCpn60β2) and CPNB3 (AtCpn60β3), while the functional partners of CPNA1 are CPNB1 (AtCpn60β1) and CPNB2. We also revealed that the functional chaperonin containing CPNA2 could assist the folding of a specific substrate, KASI (β-ketoacyl-[acyl carrier protein] synthase I), and that the KASI protein level was remarkably reduced due to loss-of-function of CPNA2. Furthermore, the reduction in the KASI protein level was shown to be the possible cause for the arrest of cpna2 embryos. Our findings indicate that the two Cpn60α subunits in Arabidopsis play different roles during embryo development through forming distinct chaperonins with specific AtCpn60β to assist the folding of particular substrates, thus providing novel insights into functional divergence of Cpn60α subunits in plants. Chaperonins are large oligomeric complexes that are involved in the folding and assembly of numerous proteins in various species. In contrast to other types of chaperonins, chloroplast chaperonins are characterized by the hetero-oligomeric structure composed of two unique types of subunits, Cpn60α and Cpn60β, each of which is present in two or more paralogous forms in most of higher plants. However, the functional significance underlying the wide array of subunit types and complex oligomeric arrangement remains largely unknown. Here, we investigated the role of the minor Cpn60α subunit AtCpn60α2 in Arabidopsis embryo development, and found that AtCpn60α2 is important for the transition of globular embryos to heart-shaped embryos, whereas loss of the dominant Cpn60α subunit AtCpn60α1 affects embryonic cotyledon development. Further studies demonstrated that AtCpn60α2 could form functional chaperonins with AtCpn60β2 and AtCpn60β3 to specifically assist in folding of the substrate KASI, which is important for the formation of heart-shaped embryos. Our results suggest that duplication of Cpn60α genes in higher plants can increase the potential number of chloroplast chaperonin substrates and provide chloroplast chaperonins with more roles in plant growth and development, thus revealing the relationship between duplication and functional specialization of chaperonin genes.
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DOI：
10.1073/pnas.94.8.3571
发表时间：
1997-04-15
影响因子：
11.1
作者：
Buckle, AM;Zahn, R;Fersht, AR
通讯作者：
Fersht, AR
影响因子：
3.5
作者：
Aronsson, H;Jarvis, P
通讯作者：
Jarvis, P
影响因子：
4.5
作者：
He S;Sun Y;Yang Q;Zhang X;Huang Q;Zhao P;Sun M;Liu J;Qian W;Qin G;Gu H;Qu LJ
通讯作者：
Qu LJ
影响因子：
7.2
作者：
Clough, SJ;Bent, AF
通讯作者：
Bent, AF
影响因子：
4.8
作者：
Dickson, R;Weiss, C;Viitanen, PV
通讯作者：
Viitanen, PV