U.S.-Mexico Collaborative Research: Biochemical Basis and Function of Stress-Induced Betaine Accumulation in Maize

该奖项将支持密歇根州立大学（MSU）的Andrew Hanson教授和普渡大学（Purdue University）的David Rhodes教授与墨西哥墨西哥城国立理工学院（IPN）的Claudia Lerma Ortiz教授以及墨西哥国际玉米和小麦改良中心（CIMMYT）的研究人员合作进行研究。研究人员打算验证这样一种假设，即甜菜碱在草中合成对于植物组织适应水分胁迫是必要的，无论是由于干旱还是盐度。甜菜碱是在盐或干旱胁迫条件下在草和藜足类（菠菜和甜菜以及许多杂草）中合成和积累的。在藜足类动物中，甜菜碱合成酶已经被确定，甜菜碱似乎是渗透调节和应激适应的核心。在禾本科植物中，高甜菜碱积累能力已被证明与适应盐碱或干旱条件广泛相关，但甜菜碱的生物合成途径和生理功能都不清楚。研究人员打算利用玉米平行研究a)甜菜碱的生物合成和b)甜菜碱积累与草的整体渗透调节的关系。玉米的选择取决于两个因素：1)玉米中甜菜碱水平和渗透调节能力的遗传变异；2)玉米的耐盐性和耐旱性相对较低，这可能与这种作物中甜菜碱含量低有关。甜菜碱生物合成酶的工作将在密歇根州立大学和IPN进行，在普渡大学进行标记化合物的合成和快速原子轰击质谱（FABMS）分析。有关甜菜碱积累与渗透调节的工作将在INP与CIMMYT的研究人员合作进行。这项工作将增加我们对植物适应低水环境的理解，同时可能为进一步推进高盐和耐旱植物的基因工程提供一条明智的途径。

This award will support Professors Andrew Hanson of Michigan State University (MSU) and David Rhodes of Purdue University in a research collaboration with Professor Claudia Lerma Ortiz of the Instituto Politecnico Nacional (IPN) in Mexico City, Mexico and researchers at the Mexican International Maize and Wheat Improvement Center (CIMMYT). The investigators intend to test the hypothesis that betaine synthesis in grasses is necessary for adjustment of plant tissues to water stress, either as a result of drought or salinity. Betaine is synthesized and accumulated in grasses and chenopods (spinach and beets as well as many weeds) under salt or drought stress conditions. In chenopods, the enzymes of betaine synthesis have been identified and betaine seems to be central to osmoregulation and stress adaptation. Among grasses, high betaine-accumulating capacity has been shown to be broadly correlated with adaptation to saline or dry conditions, but neither the biosynthetic path nor the physiological function of betaine is known. The investigators intend to use maize in parallel studies of a) betaine biosynthesis and b) the relation of betaine accumulation to overall osmoregulation in a grass. The choice of maize is dictated by two factors: 1) genetic variation for both betaine level and ability to osmoregulate is available in maize; 2) maize has relatively low salt- and drought tolerance which could be associated with the low betaine levels found in this crop. Work on betaine biosynthetic enzymes will be carried out at MSU and at the IPN, with synthesis of labeled compounds and fast atom bombardment mass spectrometry (FABMS) analysis at Purdue University. Work relating betaine accumulation to osmoregulation will be conducted at INP in collaboration with researchers at CIMMYT. The proposed work will increase our understanding of plant acclimation to low-water situations, while at the same time it is likely to provide a sensible pathway to further advances in the genetic engineering of high salt- and drought tolerant plants.