School of Biological Sciences, University of East Anglia, Norwich, UK.
Plant J. 2011 Jun;66(5):863-76. doi: 10.1111/j.1365-313X.2011.04547.x. Epub 2011 Apr 4.
MicroRNAs play a key role in the control of plant development and response to adverse environmental conditions. For example, microRNA395 (miR395), which targets three out of four isoforms of ATP sulfurylase, the first enzyme of sulfate assimilation, as well as a low-affinity sulfate transporter, SULTR2;1, is strongly induced by sulfate deficiency. However, other components of sulfate assimilation are induced by sulfate starvation, so that the role of miR395 is counterintuitive. Here, we describe the regulation of miR395 and its targets by sulfate starvation. We show that miR395 is important for the increased translocation of sulfate to the shoots during sulfate starvation. MiR395 together with the SULFUR LIMITATION 1 transcription factor maintain optimal levels of ATP sulfurylase transcripts to enable increased flux through the sulfate assimilation pathway in sulfate-deficient plants. Reduced expression of ATP sulfurylase (ATPS) alone affects both sulfate translocation and flux, but SULTR2;1 is important for the full rate of sulfate translocation to the shoots. Thus, miR395 is an integral part of the regulatory circuit controlling plant sulfate assimilation with a complex mechanism of action.
MicroRNAs 在植物发育和对不利环境条件的响应中起着关键作用。例如，miR395 靶向 ATP 硫酸化酶的四个同工型中的三个，以及低亲和力硫酸盐转运体 SULTR2;1，是硫酸盐同化的第一步酶，强烈地被硫酸盐缺乏诱导。然而，硫酸盐同化的其他成分也被硫酸盐饥饿诱导，因此 miR395 的作用是违反直觉的。在这里，我们描述了硫酸盐饥饿对 miR395 及其靶标的调节。我们表明，miR395 对于硫酸盐饥饿期间硫酸盐向地上部的转运增加是重要的。miR395 与 SULFUR LIMITATION 1 转录因子一起，维持 ATP 硫酸化酶转录物的最佳水平，以在硫酸盐缺乏的植物中增加硫酸盐同化途径的通量。单独降低 ATP 硫酸化酶 (ATPS) 的表达会影响硫酸盐的转运和通量，但 SULTR2;1 对于硫酸盐向地上部的完全转运速率是重要的。因此，miR395 是调控植物硫酸盐同化的调控回路的一个组成部分，其作用机制复杂。
