Department of Abiotic Stress and Plant Pathology. CEBAS-CSIC. P.O. Box 164. Murcia, Spain.
Plant Cell Environ. 2011 May;34(5):821-36. doi: 10.1111/j.1365-3040.2011.02285.x. Epub 2011 Mar 15.
Root-to-shoot signalling via xylem sap is an important mechanism by which plants respond to stress. This signalling could be mediated by alteration in the concentrations of inorganic and/or organic molecules. The effect of salt stress on the contents of xylem sap in Brassica olarecea has been analysed by mass spectrometry in order to quantify these changes. Subcellular location of arabinogalactan proteins (AGPs) by immunogold labelling and peroxidase isozymes was also analysed by isoelectrofocusing. The xylem sap metabolome analysis demonstrated the presence of many organic compounds such as sugars, organic acids and amino acids. Of these, amino acid concentrations, particularly that of glutamine, the major amino acid in the sap, were substantially reduced by salt stress. The xylem sap proteome analysis demonstrated the accumulation of enzymes involved in xylem differentiation and lignification, such as cystein proteinases, acid peroxidases, and a putative hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl transferase under salt stress. The peroxidase isozyme pattern showed that salt stress induced a high accumulation of an acid isoform. These results suggest that xylem differentiation and lignification is induced by salt stress. The combination of different methods to analyse the xylem sap composition provides new insights into mechanisms in plant development and signalling under salt stress.
木质部汁液中的向顶信号转导是植物响应胁迫的一个重要机制。这种信号转导可以通过无机和/或有机分子浓度的变化来介导。本研究采用质谱法分析了盐胁迫对油菜木质部汁液含量的影响，以定量这些变化。通过免疫胶体金标记和过氧化物酶同工酶分析，还分析了阿拉伯半乳聚糖蛋白 (AGP) 的亚细胞定位。木质部汁液代谢组分析表明存在许多有机化合物，如糖、有机酸和氨基酸。其中，盐胁迫显著降低了氨基酸，特别是作为汁液中主要氨基酸的谷氨酸的浓度。木质部汁液蛋白质组分析表明，盐胁迫下，与木质部分化和木质素形成相关的酶，如半胱氨酸蛋白酶、酸性过氧化物酶和一种可能的羟基肉桂酰辅酶 A：莽草酸羟基肉桂酰转移酶积累。过氧化物酶同工酶图谱表明，盐胁迫诱导了一种酸性同工酶的大量积累。这些结果表明，盐胁迫诱导木质部分化和木质素形成。结合使用不同的方法分析木质部汁液组成，为植物发育和盐胁迫下信号转导的机制提供了新的见解。
