Lundmark Maria, Nilsson Lena, K Rner Camilla J, Nielsen Tom H
Section for Plant Molecular Biology, VKR centre Pro-Active Plants, Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.
Funct Plant Biol. 2011 Feb;38(2):151-162. doi: 10.1071/FP10081.
A proper concentration and turnover of inorganic phosphate (Pi) is essential to maintain cellular processes. Consequently, plants have mechanisms to control Pi homeostasis and to alleviate Pi limitation. The MYB-related transcription factor, PHR1, is important for gene induction during Pi starvation. PHR1 belongs to a family, characterised by the presence of a GARP- and a coiled coil domain. We propose that this family, with 15 members in Arabidopsis thaliana (L.) Heynh., be termed the GCC-family. In this study, transgenic plants overexpressing one member, GCC7, and a T-DNA knockout mutant, gcc7, are characterised. We find overexpressor plants to accumulate more Pi in shoots, irrespective of the Pi supply. Therefore, GCC7 was characterised in relation to Pi starvation. We conclude that GCC7 is not strictly required for a P-starvation response since the gcc7 mutant responds to Pi limitation. However, overexpression of GCC7 strongly interferes with the P-starvation response, abolishing induction of several P-responsive genes including AT4, IPS1 and several P-transporter genes, whereas GCC7 does not directly interfere with the PHR1 (GCC1) dependent regulation of miR399d. Thus GCC7 influences P-accumulation and P-dependent gene regulation, but GCC7 has a function entirely different from PHR1.
适当浓度的无机磷酸盐（Pi）周转对于维持细胞过程至关重要。因此，植物具有控制Pi稳态和缓解Pi限制的机制。与MYB相关的转录因子PHR1在Pi饥饿期间对基因诱导很重要。PHR1属于一个家族，其特征是存在一个GARP结构域和一个卷曲螺旋结构域。我们建议将拟南芥（L.）Heynh.中具有15个成员的这个家族称为GCC家族。在本研究中，对过表达一个成员GCC7的转基因植物和一个T-DNA敲除突变体gcc7进行了表征。我们发现过表达植株的地上部积累更多的Pi，与Pi供应无关。因此，对GCC7在Pi饥饿方面进行了表征。我们得出结论，由于gcc7突变体对Pi限制有反应，所以GCC7对于P饥饿反应不是严格必需的。然而，GCC7的过表达强烈干扰P饥饿反应，消除了包括AT4、IPS1和几个P转运蛋白基因在内的几个P响应基因的诱导，而GCC7并不直接干扰PHR1（GCC1）对miR399d的依赖性调控。因此，GCC7影响P积累和P依赖性基因调控，但GCC7具有与PHR1完全不同的功能。
