Gómez-Ros Laura V, Gabaldón Carlos, López Núñez-Flores María José, Gutiérrez Jorge, Herrero Joaquín, Zapata José Miguel, Sottomayor Mariana, Cuello Juan, Ros Barceló Alfonso
Department of Plant Biology, University of Murcia, 30100, Murcia, Spain.
Planta. 2012 Aug;236(2):327-42. doi: 10.1007/s00425-012-1604-3. Epub 2012 Feb 24.
NO and H2O2 are important biological messengers in plants. They are formed during xylem differentiation in Zinnia elegans and apparently play important roles during the xylogenesis. To ascertain the responsiveness of the Z. elegans peroxidase (ZePrx) to these endogenous signals, the effects of NO and H2O2 on ZePrx were studied. The results showed that ZePrx is up-regulated by NO and H2O2, as confirmed by RT-qPCR, and that its promoter contains multiple copies of all the putative cis-elements (ACGT box, OCS box, OPAQ box, L1BX, MYCL box and W box) known to confer regulation by NO and H2O2. Like other OCS elements, the OCS element of ZePrx contains the sequence TACG that is recognized by OBF5, a highly conserved bZIP transcription factor, and the 10 bp sequence, ACAaTTTTGG, which is recognized by OBP1, a Dof domain protein that binds down-stream the OCS element. Furthermore, the ZePrx OCS element is flanked by two CCAAT-like boxes, and encloses one auxin-responsive ARFAT element and two GA3-responsive Pyr boxes. Results also showed that ZePrx may be described as the first protein to be up-regulated by NO and H2O2, whose mRNA contains several short-longevity conferring elements, such as a downstream (DST) sequence analogous to the DSTs contained in the highly unstable SAUR transcripts. The presence of these regulatory elements strongly suggests that ZePrx is finely regulated, as one may expect from an enzyme that catalyzes the last irreversible step of the formation of lignins, the major irreversible sink for the photosynthetically fixed CO2.
一氧化氮（NO）和过氧化氢（H₂O₂）是植物中重要的生物信使。它们在百日草木质部分化过程中形成，显然在木质部形成过程中发挥重要作用。为了确定百日草过氧化物酶（ZePrx）对这些内源性信号的反应，研究了NO和H₂O₂对ZePrx的影响。结果表明，RT-qPCR证实ZePrx被NO和H₂O₂上调，并且其启动子包含所有已知的假定顺式元件（ACGT盒、OCS盒、OPAQ盒、L1BX、MYCL盒和W盒）的多个拷贝，这些元件可通过NO和H₂O₂进行调控。与其他OCS元件一样，ZePrx的OCS元件包含被高度保守的bZIP转录因子OBF5识别的序列TACG，以及被结合在OCS元件下游的Dof结构域蛋白OBP1识别的10 bp序列ACAaTTTTGG。此外，ZePrx的OCS元件两侧有两个类似CCAAT的盒子，并包围一个生长素响应性ARFAT元件和两个GA₃响应性Pyr盒子。结果还表明，ZePrx可能被描述为第一个被NO和H₂O₂上调的蛋白质，其mRNA包含几个赋予短寿命的元件，例如类似于高度不稳定的SAUR转录本中所含DST的下游（DST）序列。这些调控元件的存在强烈表明ZePrx受到精细调控，这正如人们对催化木质素形成的最后不可逆步骤的酶所预期的那样，木质素是光合固定CO₂的主要不可逆汇。
