Harding Scott A, Jiang Hongying, Jeong Mijeong Lee, Casado Fanny L, Lin Han-Wei, Tsai Chung-Jui
Biotechnology Research Center, School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931, USA.
Tree Physiol. 2005 Dec;25(12):1475-86. doi: 10.1093/treephys/25.12.1475.
Regulation of leaf condensed tannins (CT) and salicylate-derived phenolic glycosides (PG) in fast- and slow-growing cottonwood backcrosses was analyzed by metabolic profiling and cDNA microarray hybridization. Seven hybrid lines of Populus fremontii L. and P. angustifolia James exhibiting growth/CT-PG phenotypes ranging from fast/low (Lines 18 and 1979) to slow/high (Lines 1012 and RL2) and intermediate (Lines NUL, 3200 and RM5) were investigated. Methanol-extractable leaf metabolites were analyzed by gas chromatography-mass spectrometry, and the results evaluated by principal component analysis. The hybrid lines formed separate clusters based on their primary metabolite profiles, with cluster arrangement also reflecting differences in CT-PG phenotype. Nitrogen (N) supply was manipulated to alter CT-PG partitioning and to obtain molecular insights into how primary metabolism interfaces with CT-PG accumulation. Three backcross lines (RM5, 1012, 18) exhibiting differential CT-PG responses to a 10-day hydroponic N-deprivation treatment were chosen for metabolite and gene expression analyses. The fast- growing Line 18 showed a minimal CT-PG response to N deprivation, and a reduction in photosynthetic gene expression. Line 1012 exhibited a strong phenylpropanoid response to N deprivation, including a doubling in phenylalanine ammonia-lyase (PAL) gene expression, and a shift from CT accumulation in the absence of stress toward PG accumulation under N-deprivation conditions. Amino acid concentrations were depressed in Lines 18 and 1012, as was expression of nitrate-sensitive genes coding for transketolase (TK), and malate dehydrogenase (MDH). Genes associated with protein synthesis and fate were down-regulated in Line 1012 but not in Line 18. Line RM5 exhibited a comparatively large increase in CT in response to N deprivation, but did not sustain decreases in amino acid concentrations, or changes in PAL, TK or MDH gene expression. Molecular characterization of the variable CT-PG responses shows promise for the identification and future testing of candidate genes for CT-PG trait selection or manipulation.
通过代谢谱分析和cDNA微阵列杂交，对速生和慢生三角叶杨回交后代叶片中缩合单宁（CT）和水杨酸衍生的酚糖苷（PG）的调控进行了分析。研究了7个弗里蒙特杨（Populus fremontii L.）和狭叶杨（P. angustifolia James）的杂交品系，它们表现出从速生/低（品系18和1979）到慢生/高（品系1012和RL2）以及中间型（品系NUL、3200和RM5）的生长/CT-PG表型。采用气相色谱-质谱联用技术分析甲醇可提取的叶片代谢产物，并通过主成分分析对结果进行评估。杂交品系根据其初级代谢产物谱形成了不同的聚类，聚类排列也反映了CT-PG表型的差异。通过控制氮（N）供应来改变CT-PG的分配，并从分子层面深入了解初级代谢与CT-PG积累之间的相互作用。选择了3个回交品系（RM5、1012、18），它们对为期10天的水培缺氮处理表现出不同的CT-PG反应，用于代谢产物和基因表达分析。速生品系18对缺氮处理的CT-PG反应最小，光合基因表达下降。品系1012对缺氮处理表现出强烈的苯丙烷类反应，包括苯丙氨酸解氨酶（PAL）基因表达增加一倍，并且在无胁迫条件下从CT积累转变为缺氮条件下的PG积累。品系18和1012中的氨基酸浓度降低，编码转酮醇酶（TK）和苹果酸脱氢酶（MDH）的硝酸盐敏感基因的表达也降低。与蛋白质合成和命运相关的基因在品系1012中下调，但在品系18中未下调。品系RM5对缺氮处理的CT反应相对较大，但氨基酸浓度没有持续下降，PAL、TK或MDH基因表达也没有变化。可变CT-PG反应的分子特征为CT-PG性状选择或操纵的候选基因的鉴定和未来测试带来了希望。
