Molecular analysis of physiological responses to changes in nitrogen in a marine macroalga, Porphyra yezoensis (Rhodophyta)
Molecular analysis of physiological responses to changes in nitrogen in a marine macroalga, Porphyra yezoensis (Rhodophyta)
复制标题
DOI：
10.1007/s10565-007-9053-7
复制
发表时间：
2008-12-01
影响因子：
6.1
通讯作者：
Amano, H.
中科院分区：
文献类型：
--
作者：
Kakinuma, M.;Coury, D. A.;Amano, H.
条斑紫菜（Porphyrayezoensis）是日本重要的经济作物。在日本，海苔的栽培经常受到“iroochi”爆发的影响，这是由于培养区域中无机营养物的减少而导致的菌体变色，这反过来又减少了菌体中光合色素的量。用无机氮处理菌体可以逆转Iroochi。在本文中，我们报告了三个条斑紫菜基因，硝酸盐转运蛋白（PyNRT 2）和两个尿素转运蛋白（PyUT 1和PyUT 2），这可能涉及逆转iroochi的特征。PyNRT 2蛋白的预测长度为479个氨基酸（AA），而PyUT 1和PyUT 2分别为740和680个AA。PyNRT 2与来自有色植物的NRT 2比来自披衣植物和高等植物的NRT更相似。两个条斑紫菜UTs的氨基酸同源性为56%，与高等植物和酵母DUR 3蛋白的亲缘关系最近，DUR 3蛋白属于钠溶质同向转运蛋白家族的一个亚家族。AA序列的疏水性图显示PyNRT 2、PyUT 1和PyUT 2分别包括12、15和16个跨膜结构域。Southern杂交分析表明条斑紫菜基因组中含有一个NRT 2编码基因和至少4个UT编码基因。PyNRT 2和PyUT基因的表达分析表明，PyNRT 2基因的信使RNA水平在硝酸盐饥饿条件下48 h后达到最大值，然后恢复到组成型水平，而PyUT基因的表达诱导成比例的处理时间在硝酸盐饥饿条件下。这些结果表明，PyNRT 2和PyUT负责在低外部硝酸盐浓度下运行的高亲和力硝酸盐/尿素转运系统。
The rhodophyte seaweed Porphyra yezoensis, known more commonly world-wide as "nori", is an important commercial crop in Japan. Cultivation of nori in Japan is often affected by outbreaks of "iroochi", a discoloration of the thalli due to a decrease in inorganic nutrients in the culture area that in turn decreases the amount of photosynthetic pigments in the thalli. Treating thalli with inorganic nitrogen can reverse iroochi. In this paper, we report on the characterization of three P. yezoensis genes, a nitrate transporter (PyNRT2) and two urea transporters (PyUT1 and PyUT2), which may be involved in reversing iroochi. The predicted length of the PyNRT2 protein was 479 amino acids (AA), while PyUT1 and PyUT2 were 740 and 680 AA, respectively. PyNRT2 was more similar to NRT2 from a chromophyte than to NRTs from Chlamydomonas and higher plants. The two P. yezoensis UTs had 56% AA identity to each other, and showed the closest relationship to higher plant and yeast DUR3 proteins which formed a subfamily of the sodium-solute symporter protein family. Hydrophobicity plots of the AA sequences showed that the PyNRT2, PyUT1, and PyUT2 included 12, 15, and 16 transmembrane domains, respectively. Southern blot analysis indicated that the P. yezoensis genome has a single NRT2-encoding gene and at least four UT-encoding genes. Expression analysis of PyNRT2 and PyUT genes showed that the messenger RNA level of the PyNRT2 gene reached a maximum after 48 h in the nitrate starvation condition and was then restored to the constitutive level, while expression of the PyUT genes was induced in proportion to treatment times in the nitrate starvation condition. These results suggest that the PyNRT2 and PyUT are responsible for the high-affinity nitrate/urea transport systems that operate under low external nitrate concentrations.