Raab Sabine, Toth Zsolt, de Groot Christian, Stamminger Thomas, Hoth Stefan
Molekulare Pflanzenphysiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, 91058 Erlangen, Germany.
Planta. 2006 Sep;224(4):900-14. doi: 10.1007/s00425-006-0282-4. Epub 2006 Apr 22.
The phytohormone abscisic acid (ABA) regulates essential growth and developmental processes in plants. Recently, RNA-binding proteins have been described as components of ABA signaling during germination. We have identified ten ABA-regulated RNA-binding proteins in Arabidopsis seedlings. Among those genes, AtCSP41B and cpRNP29 are highly expressed in seedlings. Using promoter:reporter gene analyses, we showed that both AtCSP41B and cpRNP29 were in particular expressed in photosynthetically active organs like green cotyledons, leaves, and petioles. The analysis of CFP-fusion proteins demonstrates that cpRNP29 localized to chloroplasts and AtCSP41B to chloroplasts and stromules. Whereas RNA-binding of cpRNP29 has previously been shown, we demonstrated through in vitro RNA-binding assays that recombinant AtCSP41B binds to RNA, and that chloroplast petD RNA can serve as a target of AtCSP41B. Developmental or environmental stimuli affected the expression of AtCSP41B and cpRNP29 in seedlings. Both genes were repressed during senescence, but only AtCSP41B was significantly repressed upon water stress. In addition, AtCSP41B and cpRNP29 exhibited low expression in etiolated seedlings compared to green seedlings, and cpRNP29 was regulated during the day photoperiod. Homozygous T-DNA insertion lines were isolated, characterized on the molecular level, and monitored for phenotypic changes. Taken together, the data show that both proteins are regulated during processes that are known to involve ABA signaling. Their localization in chloroplasts and RNA-binding activity suggest a role in chloroplast RNA metabolism in Arabidopsis seedlings.
植物激素脱落酸（ABA）调控植物中重要的生长和发育过程。最近，RNA结合蛋白已被描述为种子萌发过程中ABA信号传导的组成部分。我们在拟南芥幼苗中鉴定出了10种受ABA调控的RNA结合蛋白。在这些基因中，AtCSP41B和cpRNP29在幼苗中高表达。通过启动子：报告基因分析，我们发现AtCSP41B和cpRNP29特别在光合活性器官如绿色子叶、叶片和叶柄中表达。对CFP融合蛋白的分析表明，cpRNP29定位于叶绿体，AtCSP41B定位于叶绿体和叶绿体小管。虽然之前已显示cpRNP29具有RNA结合能力，但我们通过体外RNA结合试验证明重组AtCSP41B能与RNA结合，并且叶绿体petD RNA可作为AtCSP41B的靶标。发育或环境刺激会影响幼苗中AtCSP41B和cpRNP29的表达。这两个基因在衰老过程中受到抑制，但只有AtCSP41B在水分胁迫下受到显著抑制。此外，与绿色幼苗相比，AtCSP41B和cpRNP29在黄化幼苗中表达较低，并且cpRNP29在白天光周期中受到调控。分离出纯合的T-DNA插入系，在分子水平上进行表征，并监测其表型变化。综上所述，数据表明这两种蛋白在已知涉及ABA信号传导的过程中受到调控。它们在叶绿体中的定位和RNA结合活性表明其在拟南芥幼苗叶绿体RNA代谢中发挥作用。
