Department of Agronomy, National Chung Hsing University, Taichung 402, Taiwan.
Plant Physiol Biochem. 2011 Oct;49(10):1147-54. doi: 10.1016/j.plaphy.2011.07.003. Epub 2011 Jul 23.
Proline accumulation is responsible for stress adaptation in many plants. To distinguish the involvement of two proline synthetic pathways, the virus induced gene silencing (VIGS) system that silenced the expression of genes encoding Δ(1)-pyrroline-5-carboxylate synthetase (P5CS; EC:1.5.1.12) and ornithine-δ-aminotransferase (OAT; EC 2.6.1.13) was performed, separately or concomitantly, in four-week-old Nicotiana benthamiana. Leaf discs of VIGS-treated tobacco were subjected to the treatment of drought, abscisic acid (ABA), or polyethylene glycol (PEG). The treated leaf discs were then collected for the determination of mRNA, chlorophyll, proline and polyamine level. Under drought stress or PEG treatment, most proline accumulation was inhibited in P5CS-silenced plants and only a small portion was inhibited in OAT-silenced plants under drought stress and no inhibition was observed under PEG treatment. Under ABA treatment, proline accumulation was inhibited completely in P5CS-silenced plants but unaffected in OAT-silenced plants. The degradation of chlorophyll was enhanced in P5CS-silenced plants but retarded in OAT-silenced plants under PEG treatment. Under ABA treatment, the degradation of chlorophyll was unaffected in both P5CS-silenced and OAT-silenced plants. The increase of polyamine level was unaffected in P5CS-silenced plants but increased in OAT-silenced plants under PEG treatment. Under ABA treatment, the increase of polyamine level was unaffected in P5CS-silenced plants but the polyamine level was increased later in OAT-silenced plants. Therefore, P5CS plays a major role in proline accumulation under drought, PEG, or ABA treatment, while OAT plays a minor role in drought or PEG treatment and does not participate in ABA treatment. OAT appears to have a close relationship with the regulation of polyamine levels in PEG and ABA treatments.
脯氨酸积累是许多植物适应胁迫的原因。为了区分两条脯氨酸合成途径的参与，分别或同时利用病毒诱导的基因沉默（VIGS）系统沉默编码 Δ(1)-吡咯啉-5-羧酸合成酶（P5CS；EC：1.5.1.12）和鸟氨酸 δ-氨基转移酶（OAT；EC 2.6.1.13）的基因表达，对四叶期的本氏烟进行处理。用干旱、脱落酸（ABA）或聚乙二醇（PEG）处理 VIGS 处理的烟叶片。然后收集处理过的叶片圆盘，用于测定 mRNA、叶绿素、脯氨酸和多胺水平。在干旱胁迫或 PEG 处理下，P5CS 沉默植株中大部分脯氨酸积累受到抑制，而 OAT 沉默植株中只有一小部分受到抑制，且在 PEG 处理下没有抑制；在 ABA 处理下，P5CS 沉默植株中脯氨酸积累完全受到抑制，而 OAT 沉默植株不受影响。在 PEG 处理下，P5CS 沉默植株中叶绿素降解增强，而 OAT 沉默植株中叶绿素降解减缓。在 ABA 处理下，P5CS 沉默和 OAT 沉默植株中叶绿素降解均不受影响。在 P5CS 沉默植株中，多胺水平的增加不受影响，但在 PEG 处理下，OAT 沉默植株中的多胺水平增加。在 ABA 处理下，P5CS 沉默植株中多胺水平的增加不受影响，但在 OAT 沉默植株中多胺水平的增加较晚。因此，在干旱、PEG 或 ABA 处理下，P5CS 在脯氨酸积累中起主要作用，而 OAT 在干旱或 PEG 处理中作用较小，且不参与 ABA 处理。OAT 似乎与 PEG 和 ABA 处理中多胺水平的调节密切相关。
