Dallmier K A, Stewart C R
Department of Botany, Iowa State University, Ames, Iowa 50011.
Plant Physiol. 1992 Jun;99(2):762-4. doi: 10.1104/pp.99.2.762.
Plant responses to drought stress include proline and abscisic acid (ABA) accumulation. Proline dehydrogenase (PDH) (EC 1.4.3) is the first enzyme in the proline oxidation pathway, and its activity has been shown to decline in response to water stress (PJ Rayapati, CR Stewart [1991] Plant Physiol 95: 787-791). In this investigation, we determined whether ABA treatment affects PDH activity in a manner similar to drought stress in maize (Zea mays L.) seedlings. Four exogenous ABA treatments (0, 11, 33, and 100 micromolar ABA) were applied to well-watered maize seedlings. Mitochondria were isolated and PDH was solubilized using Nonidet P-40. PDH activity was measured by the reduction of iodonitrotetrazolium violet under proline-dependent conditions. There was no effect of ABA on PDH activity at 33 and 100 micromolar ABA, but there was a 38% decline at 11 micromolar. This decline was less than the 69% reduction in activity under drought stress. Endogenous ABA determinations and plant growth rate showed that ABA entered the plant and was affecting metabolic processes. ABA treatments had a small effect on shoot and root proline concentration, whereas drought stress caused a 220% increase in root tissues. We conclude that ABA is not part of the pathway linking drought stress and decreased PDH activity.
植物对干旱胁迫的响应包括脯氨酸和脱落酸（ABA）的积累。脯氨酸脱氢酶（PDH）（EC 1.4.3）是脯氨酸氧化途径中的首个酶，其活性已被证明会响应水分胁迫而下降（PJ·拉亚帕蒂、CR·斯图尔特[1991]《植物生理学》95：787 - 791）。在本研究中，我们测定了ABA处理是否以类似于玉米（Zea mays L.）幼苗干旱胁迫的方式影响PDH活性。对充分浇水的玉米幼苗施加四种外源ABA处理（0、11、33和100微摩尔ABA）。分离线粒体并用诺乃洗涤剂P - 40溶解PDH。在脯氨酸依赖的条件下，通过碘硝基四氮唑紫的还原测定PDH活性。在33和100微摩尔ABA浓度下，ABA对PDH活性没有影响，但在11微摩尔时活性下降了38%。这种下降小于干旱胁迫下69%的活性降低。内源ABA测定和植物生长速率表明ABA进入了植物并正在影响代谢过程。ABA处理对地上部和根部的脯氨酸浓度影响较小，而干旱胁迫导致根部组织中脯氨酸浓度增加了220%。我们得出结论，ABA不是连接干旱胁迫和PDH活性降低途径的一部分。
