Bogusz D, Appleby C A, Landsmann J, Dennis E S, Trinick M J, Peacock W J
Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, Canberra, A.C.T., Australia.
Nature. 1988 Jan 14;331(6152):178-80. doi: 10.1038/331178a0.
Haemoglobin has previously been recorded in plants only in the nitrogen-fixing nodules formed by symbiotic association between Rhizobium or Frankia and legume or non-legume hosts. Structural similarities amongst these and animal haemoglobins at the protein and gene level suggested a common evolutionary origin. This suggests that haemoglobin genes, inherited from an ancestor common to plants and animals, might be present in all plants. We report here the isolation of a haemoglobin gene from Trema tomentosa, a non-nodulating relative of Parasponia (Ulmaceae). The gene has three introns located at positions identical to those in the haemoglobin genes of nodulating plant species, strengthening the case for a common origin of all plant haemoglobin genes. The data argue strongly against horizontal haemoglobin gene transfer from animals to plants. The Trema gene has a tissue-specific pattern of transcription and translation, producing monomeric haemoglobin in Trema roots. We have also found that the Parasponia haemoglobin gene is transcribed in roots of non-nodulated plants. These results suggest that haemoglobin has a role in the respiratory metabolism of root cells of all plant species. We propose that its special role in nitrogen-fixing nodules has required adaptation of the haemoglobin-gene regulation pathway, to give high expression in the specialized environment of the nodule.
血红蛋白此前仅在由根瘤菌或弗兰克氏菌与豆科或非豆科宿主共生形成的固氮根瘤中在植物体内被发现。这些血红蛋白与动物血红蛋白在蛋白质和基因水平上的结构相似性表明它们有着共同的进化起源。这意味着从动植物的共同祖先遗传而来的血红蛋白基因可能存在于所有植物中。我们在此报告从绒毛山黄麻（榆科，与帕拉豆属有亲缘关系但不形成根瘤）中分离出一个血红蛋白基因。该基因有三个内含子，其位置与形成根瘤的植物物种的血红蛋白基因中的内含子位置相同，这进一步证明了所有植物血红蛋白基因有共同起源。这些数据有力地反驳了血红蛋白基因从动物水平转移到植物的观点。绒毛山黄麻基因具有组织特异性的转录和翻译模式，在其根部产生单体血红蛋白。我们还发现帕拉豆属的血红蛋白基因在未形成根瘤的植物根部也有转录。这些结果表明血红蛋白在所有植物物种根细胞的呼吸代谢中发挥作用。我们认为它在固氮根瘤中的特殊作用需要对血红蛋白基因调控途径进行适应性调整，以便在根瘤的特殊环境中实现高表达。
