Table_1_PhDHS Is Involved in Chloroplast Development in Petunia.doc

Deoxyhypusine synthase (DHS) is encoded by a nuclear gene and is the key enzyme involved in the post-translational activation of the eukaryotic translation initiation factor eIF5A. DHS plays important roles in plant growth and development. To gain a better understanding of DHS, the petunia (Petunia hybrida) PhDHS gene was isolated, and the role of PhDHS in plant growth was analyzed. PhDHS protein was localized to the nucleus and cytoplasm. Virus-mediated PhDHS silencing caused a sectored chlorotic leaf phenotype. Chlorophyll levels and photosystem II activity were reduced, and chloroplast development was abnormal in PhDHS-silenced leaves. In addition, PhDHS silencing resulted in extended leaf longevity and thick leaves. A proteome assay revealed that 308 proteins are upregulated and 266 proteins are downregulated in PhDHS-silenced plants compared with control, among the latter, 21 proteins of photosystem I and photosystem II and 12 thylakoid (thylakoid lumen and thylakoid membrane) proteins. In addition, the mRNA level of PheIF5A-1 significantly decreased in PhDHS-silenced plants, while that of another three PheIF5As were not significantly affected in PhDHS-silenced plants. Thus, silencing of PhDHS affects photosynthesis presumably as an indirect effect due to reduced expression of PheIF5A-1 in petunia.
Significance:PhDHS-silenced plants develop yellow leaves and exhibit a reduced level of photosynthetic pigment in mesophyll cells. In addition, arrested development of chloroplasts is observed in the yellow leaves.

脱氧羟腐胺赖氨酸合酶（Deoxyhypusine synthase, DHS）由核基因编码，是参与真核翻译起始因子eIF5A翻译后激活的关键酶。DHS在植物生长发育中发挥重要作用。为深入解析DHS的生物学功能，研究人员克隆得到矮牵牛（Petunia hybrida）的PhDHS基因，并分析了其在植物生长中的功能。PhDHS蛋白定位于细胞核与细胞质中。病毒介导的PhDHS基因沉默会导致植株出现斑驳型褪绿叶片表型。沉默植株的叶绿素含量与光系统II（photosystem II）活性均显著降低，且叶片中叶绿体发育异常。此外，PhDHS基因沉默还会导致叶片寿命延长、叶片增厚。蛋白质组分析结果显示，与对照植株相比，PhDHS沉默植株中有308个蛋白上调表达、266个蛋白下调表达，其中下调表达的蛋白包含21个光系统I与光系统II相关蛋白，以及12个类囊体（类囊体腔与类囊体膜）相关蛋白。另外，PhDHS沉默植株中PheIF5A-1的mRNA转录水平显著下降，而其余3个PheIF5A家族基因的mRNA转录水平未发生显著变化。综上，矮牵牛中PhDHS基因沉默可通过降低PheIF5A-1的表达，间接影响植物的光合作用过程。
研究意义：PhDHS沉默植株会形成黄色叶片，且叶肉细胞中的光合色素水平降低；此外，黄色叶片中可观察到叶绿体发育受阻。