Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
J Plant Physiol. 2011 Jul 1;168(10):1106-13. doi: 10.1016/j.jplph.2010.12.007. Epub 2011 Feb 18.
The expression profiles of Δ9 stearoyl-acyl carrier protein desaturase (SAD1 and SAD2) and type 3 metallothionein (MT3-A and MT3-B) were investigated in seedlings of oil palm (Elaeis guineensis) artificially inoculated with the pathogenic fungus Ganoderma boninense and the symbiotic fungus Trichoderma harzianum. Expression of SAD1 and MT3-A in roots and SAD2 in leaves were significantly up-regulated in G. boninense inoculated seedlings at 21 d after treatment when physical symptoms had not yet appeared and thereafter decreased to basal levels when symptoms became visible. Our finding demonstrated that the SAD1 expression in leaves was significantly down-regulated to negligible levels at 42 and 63 d after treatment. The transcripts of MT3 genes were synthesized in G. boninense inoculated leaves at 42 d after treatment, and the analyses did not show detectable expression of these genes before 42 d after treatment. In T. harzianum inoculated seedlings, the expression levels of SAD1 and SAD2 increased gradually and were stronger in roots than leaves, while for MT3-A and MT3-B, the expression levels were induced in leaves at 3d after treatment and subsequently maintained at same levels until 63d after treatment. The MT3-A expression was significantly up-regulated in roots at 3d after treatment and thereafter were maintained at this level. Both SAD and MT3 expression were maintained at maximum levels or at levels higher than basal. This study demonstrates that oil palm was able to distinguish between pathogenic and symbiotic fungal interactions, thus resulting in different transcriptional activation profiles of SAD and MT3 genes. Increases in expression levels of SAD and MT3 would lead to enhanced resistance against G. boninense and down-regulation of genes confer potential for invasive growth of the pathogen. Differences in expression profiles of SAD and MT3 relate to plant resistance mechanisms while supporting growth enhancing effects of symbiotic T. harzianum.
研究了人工接种病原菌波氏角担菌和共生真菌木霉后油棕幼苗中Δ9 硬脂酰-酰基载体蛋白去饱和酶（SAD1 和 SAD2）和 3 型金属硫蛋白（MT3-A 和 MT3-B）的表达谱。在处理后 21 天，当尚未出现物理症状时，根中 SAD1 和 MT3-A 的表达以及叶片中 SAD2 的表达在波氏角担菌接种的幼苗中显著上调，此后当症状可见时，表达水平下降到基础水平。我们的发现表明，在处理后 42 和 63 天时，叶片中 SAD1 的表达显著下调至可忽略水平。在处理后 42 天时，MT3 基因的转录物在波氏角担菌接种的叶片中合成，并且在处理后 42 天之前未检测到这些基因的表达。在木霉接种的幼苗中，SAD1 和 SAD2 的表达水平逐渐增加，在根部比叶片中更强，而对于 MT3-A 和 MT3-B，在处理后 3 天诱导叶片表达，随后在 63 天处理后维持相同水平。MT3-A 的表达在处理后 3 天在根部显著上调，此后维持在该水平。SAD 和 MT3 的表达均保持在最高水平或高于基础水平。这项研究表明，油棕能够区分病原菌和共生真菌的相互作用，从而导致 SAD 和 MT3 基因的不同转录激活谱。SAD 和 MT3 表达水平的增加将导致对波氏角担菌的抗性增强，并且下调赋予病原体侵袭生长潜力的基因。SAD 和 MT3 的表达谱差异与植物抗性机制有关，同时支持共生木霉的生长促进作用。
