Kwak Man Sup, Min Sung Ran, Lee Si-Myung, Kim Kyung-Nam, Liu Jang Ryol, Paek Kyung-Hee, Shin Jeong Sheop, Bae Jung Myung
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Plant Physiol. 2007 Sep;145(1):277-89. doi: 10.1104/pp.107.102095. Epub 2007 Jul 27.
In this study, a tobacco (Nicotiana tabacum 'Xanthi') ADP-glucose pyrophosphorylase cDNA (NtAGP) was isolated from a flower bud cDNA library and the role of NtAGP in the growth of the floral organ was characterized. The expression of NtAGP was high in the sepal, moderate in the carpel and stamen, and low in the petal tissues. NtAGP-antisense plants produced flowers with abnormal petal limbs due to the early termination of the expansion growth of the petal limbs between the corolla lobes. Microscopic observation of the limb region revealed that cell expansion was limited in NtAGP-antisense plants but that cell numbers remained unchanged. mRNA levels of NtAGP, ADP-glucose pyrophosphorylase activity, and starch content in the sepal tissues of NtAGP-antisense plants were reduced, resulting in significantly lower levels of sugars (sucrose, glucose, and fructose) in the petal limbs. The feeding of these sugars to flower buds of the NtAGP-antisense plants restored the expansion growth in the limb area between the corolla lobes. Expansion growth of the petal limb between the corolla lobes was severely arrested in 'Xanthi' flowers from which sepals were removed, indicating that sepal carbohydrates are essential for petal limb expansion growth. These results demonstrate that NtAGP plays a crucial role in the morphogenesis of petal limbs in 'Xanthi' through the synthesis of starch, which is the main carbohydrate source for expansion growth of petal limbs, in sepal tissues.
在本研究中，从花芽cDNA文库中分离出烟草（Nicotiana tabacum 'Xanthi'）ADP - 葡萄糖焦磷酸化酶cDNA（NtAGP），并对NtAGP在花器官生长中的作用进行了表征。NtAGP在萼片中表达量高，在心皮和雄蕊中表达量中等，在花瓣组织中表达量低。NtAGP反义植株产生的花，其花瓣边缘异常，这是由于花冠裂片之间花瓣边缘的扩展生长提前终止所致。对边缘区域的显微镜观察表明，NtAGP反义植株中的细胞扩展受到限制，但细胞数量保持不变。NtAGP反义植株萼片组织中NtAGP的mRNA水平、ADP - 葡萄糖焦磷酸化酶活性和淀粉含量均降低，导致花瓣边缘的糖类（蔗糖、葡萄糖和果糖）水平显著降低。将这些糖类饲喂给NtAGP反义植株的花芽，可恢复花冠裂片之间边缘区域的扩展生长。从去除萼片的“Xanthi”花中，花冠裂片之间花瓣边缘的扩展生长严重受阻，这表明萼片碳水化合物对于花瓣边缘的扩展生长至关重要。这些结果表明，NtAGP通过在萼片组织中合成淀粉（花瓣边缘扩展生长的主要碳水化合物来源），在“Xanthi”花瓣边缘的形态发生中起关键作用。
