Lochmanová Gabriela, Zdráhal Zbynek, Konecná Hana, Koukalová Sárka, Malbeck Jirí, Soucek Premysl, Válková Martina, Kiran Nagavalli S, Brzobohaty Bretislav
Institute of Biophysics AS CR, v.v.i., Královopolská 135, CZ-61265, Brno, Czech Republic.
J Exp Bot. 2008;59(13):3705-19. doi: 10.1093/jxb/ern220. Epub 2008 Sep 5.
High concentrations of cytokinins (CKs) in the cultivation medium can induce partial photomorphogenesis in dark-grown Arabidopsis seedlings. However, no significant increases in endogenous CK levels have been found in de-etiolated mutants, suggesting that either parallel pathways are involved in the light and CK responses, or changes in the sensitivity to CKs occur during photomorphogenesis. Here it is shown that even modest increases in endogenous CK levels induced by transgenic expression of the CK biosynthetic gene, ipt, can lead to many typical features of light-induced de-etiolation, including inhibition of hypocotyl elongation and partial cotyledon opening. In addition, significant changes in expression of 37 proteins (mostly related to chloroplast biogenesis, a major element of light-induced photomorphogenesis) were detected by image and mass spectrometric analysis of two-dimensionally separated proteins. The identified chloroplast proteins were all up-regulated in response to increased CKs, and more than half are up-regulated at the transcript level during light-induced photomorphogenesis according to previously published transcriptomic data. Four of the up-regulated chloroplast proteins identified here have also been shown to be up-regulated during light-induced photomorphogenesis in previous proteomic analyses. In contrast, all differentially regulated mitochondrial proteins (the second largest group of differentially expressed proteins) were down-regulated. Changes in the levels of several tubulins are consistent with the observed morphological alterations. Further, 10 out of the 37 differentially expressed proteins detected have not been linked to either photomorphogenesis or CK action in light-grown Arabidopsis seedlings in previously published transcriptomic or proteomic analyses.
在培养基中高浓度的细胞分裂素（CKs）可诱导黑暗中生长的拟南芥幼苗发生部分光形态建成。然而，在去黄化突变体中未发现内源CK水平有显著增加，这表明光反应和CK反应可能涉及平行途径，或者在光形态建成过程中对CKs的敏感性发生了变化。本文表明，即使通过CK生物合成基因ipt的转基因表达使内源CK水平适度增加，也能导致光诱导去黄化的许多典型特征，包括抑制下胚轴伸长和部分子叶张开。此外，通过对二维分离蛋白质的图像和质谱分析，检测到37种蛋白质（大多与叶绿体生物发生有关，这是光诱导光形态建成的一个主要因素）的表达有显著变化。鉴定出的叶绿体蛋白质均因CKs增加而上调，根据先前发表的转录组数据，超过一半的蛋白质在光诱导光形态建成过程中在转录水平上也上调。本文鉴定出的4种上调的叶绿体蛋白质在先前的蛋白质组学分析中也已显示在光诱导光形态建成过程中上调。相反，所有差异调节的线粒体蛋白质（差异表达蛋白质的第二大组）均下调。几种微管蛋白水平的变化与观察到的形态改变一致。此外，在先前发表的转录组学或蛋白质组学分析中，在光生长的拟南芥幼苗中检测到的37种差异表达蛋白质中有10种与光形态建成或CK作用均无关联。
