Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany.
BMC Plant Biol. 2012 May 1;12:60. doi: 10.1186/1471-2229-12-60.
The N. attenuata HD20 gene belongs to the homeodomain-leucine zipper (HD-Zip) type I family of transcription factors and it has been previously associated with the regulation of ABA accumulation in leaves and the emission of benzyl acetone (BA; 4-phenyl-2-butanone) from night flowers. In this study, N. attenuata plants stably reduced in the expression of HD20 (ir-hd20) were generated to investigate the mechanisms controlling the emission of BA from night flowers.
The expression of HD20 in corollas of ir-hd20 plants was reduced by 85 to 90% compared to wild-type plants (WT) without affecting flower morphology and development. Total BA emitted from flowers of ir-hd20 plants was reduced on average by 60%. This reduction occurred mainly at the late phase of BA emission and it was correlated with 2-fold higher levels of ABA in the corollas of ir-hd20 plants. When a 2-fold decline in ABA corolla levels of these plants was induced by salt stress, BA emissions recovered to WT levels. Supplying ABA to WT flowers either through the cuticle or by pedicle feeding reduced the total BA emissions by 25 to 50%; this reduction occurred primarily at the late phase of emission (similar to the reduction observed in corollas of ir-hd20 plants). Gene expression profiling of corollas collected at 12 pm (six hours before the start of BA emission) revealed that 274 genes changed expression levels significantly in ir-hd20 plants compared to WT. Among these genes, more than 35% were associated with metabolism and the most prominent group was associated with the metabolism of aromatic compounds and phenylpropanoid derivatives.
The results indicated that regulation of ABA levels in corollas is associated with the late phase of BA emission in N. attenuata plants and that HD20 affects this latter process by mediating changes in both ABA levels and metabolic gene expression.
N. attenuata HD20 基因属于同源域亮氨酸拉链（HD-Zip）I 型家族的转录因子，先前与叶片中 ABA 积累的调节以及夜间花中苯乙酮（BA；4-苯基-2-丁酮）的排放有关。在这项研究中，生成了稳定表达 HD20 的 N. attenuata 植物（ir-hd20），以研究控制夜间花中 BA 排放的机制。
ir-hd20 植物的花冠中 HD20 的表达减少了 85%至 90%，而不影响花的形态和发育。ir-hd20 植物花朵释放的总 BA 平均减少了 60%。这种减少主要发生在 BA 排放的后期，与 ir-hd20 植物花冠中 ABA 水平升高 2 倍有关。当这些植物的 ABA 花冠水平通过盐胁迫降低 2 倍时，BA 排放恢复到 WT 水平。通过表皮或花梗喂养向 WT 花朵提供 ABA，将总 BA 排放量减少 25%至 50%；这种减少主要发生在排放的后期（类似于 ir-hd20 植物花冠中观察到的减少）。在 12 pm（BA 排放开始前六小时）收集的花冠进行基因表达谱分析显示，与 WT 相比，ir-hd20 植物中有 274 个基因的表达水平发生了显著变化。在这些基因中，超过 35%与代谢有关，最突出的一组与芳香族化合物和苯丙烷衍生物的代谢有关。
结果表明，花冠中 ABA 水平的调节与 N. attenuata 植物中 BA 排放的后期阶段有关，而 HD20 通过调节 ABA 水平和代谢基因表达的变化来影响这一后期过程。
