Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom.
Plant Physiol. 2012 Aug;159(4):1418-27. doi: 10.1104/pp.112.200584. Epub 2012 Jun 6.
C(4) photosynthesis has evolved in at least 66 lineages within the angiosperms and involves alterations to the biochemistry, cell biology, and development of leaves. The characteristic "Kranz" anatomy of most C(4) leaves was discovered in the 1890s, but the genetic basis of these traits remains poorly defined. Oat × maize addition lines allow the effects of individual maize (Zea mays; C(4)) chromosomes to be investigated in an oat (Avena sativa; C(3)) genetic background. Here, we have determined the extent to which maize chromosomes can introduce C(4) characteristics into oat and have associated any C(4)-like changes with specific maize chromosomes. While there is no indication of a simultaneous change to C(4) biochemistry, leaf anatomy, and ultrastructure in any of the oat × maize addition lines, the C(3) oat leaf can be modified at multiple levels. Maize genes encoding phosphoenolpyruvate carboxylase, pyruvate, orthophosphate dikinase, and the 2'-oxoglutarate/malate transporter are expressed in oat and generate transcripts of the correct size. Three maize chromosomes independently cause increases in vein density, and maize chromosome 3 results in larger bundle sheath cells with increased cell wall lipid deposition in oat leaves. These data provide proof of principle that aspects of C(4) biology could be integrated into leaves of C(3) crops.
C(4)光合作用至少在被子植物的 66 个谱系中进化，涉及对生物化学、细胞生物学和叶片发育的改变。大多数 C(4)叶片的特征性“Kranz”解剖结构在 19 世纪 90 年代被发现，但这些特征的遗传基础仍未得到明确界定。燕麦×玉米添加系允许在燕麦（Avena sativa；C(3)）遗传背景下研究单个玉米（Zea mays；C(4))染色体的影响。在这里，我们已经确定了玉米染色体可以在多大程度上将 C(4)特征引入燕麦中，并将任何类似 C(4)的变化与特定的玉米染色体联系起来。虽然在任何燕麦×玉米添加系中都没有表明同时发生 C(4)生物化学、叶片解剖结构和超微结构的变化，但 C(3)燕麦叶片可以在多个水平上进行修饰。编码磷酸烯醇丙酮酸羧化酶、丙酮酸、正磷酸二激酶和 2'- 酮戊二酸/苹果酸转运体的玉米基因在燕麦中表达，并产生正确大小的转录本。三个玉米染色体独立地导致叶脉密度增加，玉米染色体 3导致燕麦叶片中的束鞘细胞更大，细胞壁脂质沉积增加。这些数据提供了原理证明，即 C(4)生物学的某些方面可以整合到 C(3)作物的叶片中。
