Long Benedict M, Bahar Nur H A, Atkin Owen K
ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia.
ARC Centre of Excellence in Plant Energy Biology, Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia.
Plant Cell Environ. 2015 Nov;38(11):2263-76. doi: 10.1111/pce.12544. Epub 2015 May 12.
In intact leaves, mitochondrial populations are highly heterogeneous among contrasting cell types; how such contrasting populations respond to sustained changes in the environment remains, however, unclear. Here, we examined respiratory rates, mitochondrial protein composition and response to growth temperature in photosynthetic (mesophyll) and non-photosynthetic (epidermal) cells from fully expanded leaves of warm-developed (WD) and cold-developed (CD) broad bean (Vicia faba L.). Rates of respiration were significantly higher in mesophyll cell protoplasts (MCPs) than epidermal cell protoplasts (ECPs), with both protoplast types exhibiting capacity for cytochrome and alternative oxidase activity. Compared with ECPs, MCPs contained greater relative quantities of porin, suggesting higher mitochondrial surface area in mesophyll cells. Nevertheless, the relative quantities of respiratory proteins (normalized to porin) were similar in MCPs and ECPs, suggesting that ECPs have lower numbers of mitochondria yet similar protein complement to MCP mitochondria (albeit with lower abundance serine hydroxymethyltransferase). Several mitochondrial proteins (both non-photorespiratory and photorespiratory) exhibited an increased abundance in response to cold in both protoplast types. Based on estimates of individual protoplast respiration rates, combined with leaf cell abundance data, epidermal cells make a small but significant (2%) contribution to overall leaf respiration which increases twofold in the cold. Taken together, our data highlight the heterogeneous nature of mitochondrial populations in leaves, both among contrasting cell types and in how those populations respond to growth temperature.
在完整叶片中，线粒体群体在不同细胞类型间具有高度异质性；然而，这些不同的群体如何响应环境的持续变化仍不清楚。在此，我们检测了来自温育（WD）和冷育（CD）蚕豆（Vicia faba L.）完全展开叶片的光合（叶肉）细胞和非光合（表皮）细胞中的呼吸速率、线粒体蛋白质组成以及对生长温度的响应。叶肉细胞原生质体（MCPs）的呼吸速率显著高于表皮细胞原生质体（ECPs），两种原生质体类型均表现出细胞色素和交替氧化酶活性。与ECPs相比，MCPs含有相对更多的孔蛋白，表明叶肉细胞中线粒体表面积更大。尽管如此，呼吸蛋白的相对含量（以孔蛋白标准化）在MCPs和ECPs中相似，这表明ECPs中线粒体数量较少，但蛋白质组成与MCP线粒体相似（尽管丝氨酸羟甲基转移酶丰度较低）。两种原生质体类型中，几种线粒体蛋白（包括非光呼吸和光呼吸蛋白）在低温下丰度均增加。基于对单个原生质体呼吸速率的估计，并结合叶片细胞丰度数据，表皮细胞对叶片总呼吸的贡献虽小但显著（2%），在低温下增加两倍。综上所述，我们的数据突出了叶片中线粒体群体的异质性，包括在不同细胞类型之间以及这些群体对生长温度的响应方式上。
