Mikami Koji, Khoa Ho Viet
School of Food Industrial Sciences, Miyagi University, Hatatate 2-2-1, Sendai 982-0215, Japan.
Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-Cho, Hakodate 041-8611, Japan.
Plants (Basel). 2023 May 23;12(11):2070. doi: 10.3390/plants12112070.
Heat shock protein 70 (HSP70) is an evolutionarily conserved protein chaperone in prokaryotic and eukaryotic organisms. This family is involved in the maintenance of physiological homeostasis by ensuring the proper folding and refolding of proteins. The HSP70 family in terrestrial plants can be divided into cytoplasm, endoplasmic reticulum (ER)-, mitochondrion (MT)-, and chloroplast (CP)-localized HSP70 subfamilies. In the marine red alga , the heat-inducible expression of two cytoplasmic genes has been characterized; however, little is known about the presence of other subfamilies and their expression profiles under heat stress conditions. Here, we identified genes encoding one MT and two ER HSP70 proteins and confirmed their heat-inducible expression at 25 °C. In addition, we determined that membrane fluidization directs gene expression for the ER-, MT-, and CP-localized HSP70 proteins as with cytoplasmic HSP70s. The gene for the CP-localized HSP70 is carried by the chloroplast genome; thus, our results indicate that membrane fluidization is a trigger for the coordinated heat-driven induction of genes harbored by the nuclear and plastid genomes in . We propose this mechanism as a unique regulatory system common in the Bangiales, in which the CP-localized HSP70 is usually encoded in the chloroplast genome.
热休克蛋白70（HSP70）是原核生物和真核生物中一种进化保守的蛋白质伴侣。该家族通过确保蛋白质的正确折叠和重新折叠参与生理稳态的维持。陆生植物中的HSP70家族可分为定位于细胞质、内质网（ER）、线粒体（MT）和叶绿体（CP）的HSP70亚家族。在海洋红藻中，已对两个细胞质基因的热诱导表达进行了表征；然而，对于其他亚家族的存在及其在热胁迫条件下的表达谱知之甚少。在这里，我们鉴定了编码一种线粒体和两种内质网HSP70蛋白的基因，并证实了它们在25℃时的热诱导表达。此外，我们确定膜流化与细胞质HSP70一样，指导内质网、线粒体和叶绿体定位的HSP70蛋白的基因表达。叶绿体定位的HSP70基因由叶绿体基因组携带；因此，我们的结果表明膜流化是热驱动协调诱导核基因组和质体基因组中基因的触发因素。我们提出这种机制是红毛菜纲中常见的一种独特调节系统，其中叶绿体定位的HSP70通常由叶绿体基因组编码。
