PDF(Pubmed)
Abstract：
Salicylic acid (SA) is a stress hormone synthesized in phenylalanine ammonia-lyase (PAL) and the branching acid pathway. SA has two interconvertible forms in plants: SAG (SA O-β-glucoside) and SA (free form). The molecular mechanism of conversion of SA to SAG had been reported previously. However, which genes regulate SAG to SA remained unknown. Here, we report a cytoplasmic β-glucosidase (β-Glu) which participates in the SA pathway and is involved in the brown hull pigmentation in rice grain. In the current study, an EMS-generated mutant brown hull 1 (bh1) displayed decreased contents of SA in hulls, a lower photosynthesis rate, and high-temperature sensitivity compared to the wild type (WT). A plaque-like phenotype (brown pigmentation) was present on the hulls of bh1, which causes a significant decrease in the seed setting rate. Genetic analysis revealed a mutation in LOC_Os01g67220, which encodes a cytoplasmic Os1βGlu4. The knock-out lines displayed the phenotype of brown pigmentation on hulls and decreased seed setting rate comparable with bh1. Overexpression and complementation lines of Os1βGlu4 restored the phenotype of hulls and normal seed setting rate comparable with WT. Subcellular localization revealed that the protein of Os1βGlu4 was localized in the cytoplasm. In contrast to WT, bh1 could not hydrolyze SAG into SA in vivo. Together, our results revealed the novel role of Os1βGlu4 in the accumulation of flavonoids in hulls by regulating the level of free SA in the cellular pool.
摘要：
水杨酸（SA）是在苯丙氨酸解氨酶（PAL）和分支酸途径中合成的应激激素。SA在植物中具有两种可相互转化的形式:SAG(SAO-β-葡糖苷)和SA(游离形式)。以前已经报道了SA转化为SAG的分子机制。然而,哪些基因调节SAG至SA仍然未知。这里,我们报道了一种细胞质β-葡萄糖苷酶（β-Glu），它参与了SA途径，并参与了水稻籽粒的棕色壳色素沉着。在目前的研究中,EMS产生的突变体棕色船体1（bh1）显示船体中SA的含量降低，较低的光合作用速率，和与野生型（WT）相比的高温敏感性。bh1的壳上存在斑块状表型（棕色色素沉着），这导致结实率显着降低。遗传分析揭示LOC_Os01g67220中的突变,其编码细胞质OS1βGlu4。敲除品系在船体上显示出棕色色素沉着的表型，并且与bh1相当的结实率降低。OS1βGlu4的过表达和互补系恢复了与WT相当的船体表型和正常结实率。亚细胞定位显示OS1βGlu4蛋白定位于细胞质中。与WT相比，bh1不能在体内将SAG水解为SA。一起,我们的结果揭示了OS1βGlu4通过调节细胞池中游离SA的水平在船体中类黄酮积累中的新作用。
