ZxNHX controls Na⁺ and K⁺ homeostasis at the whole-plant level in Zygophyllum xanthoxylum through feedback regulation of the expression of genes involved in their transport.
ZxNHX controls Na⁺ and K⁺ homeostasis at the whole-plant level in Zygophyllum xanthoxylum through feedback regulation of the expression of genes involved in their transport.
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DOI：
10.1093/aob/mcu177
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发表时间：
2015-02
期刊：
影响因子：
4.2
通讯作者：
Hui-Jun Yuan;Q. Ma;Guo-Qiang Wu;Pei Wang;Jing Hu;Suo-min Wang
中科院分区：
文献类型：
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作者：
Hui-Jun Yuan;Q. Ma;Guo-Qiang Wu;Pei Wang;Jing Hu;Suo-min Wang
为了适应干旱环境，干旱盐生植物霸王（Zygophyllum xanthoxylum）通过ZxNHX将Na（+）有效地分隔到液泡中，并维持叶片中K（+）的稳定性。然而，ZxNHX在整个植物水平上控制Na（+）和K（+）稳态的功能仍不清楚。在这项研究中，ZxNHX在调控基因的表达参与Na（+）和K（+）的运输和空间分布的作用进行了研究。方法研究ZxNHX在维持Z.通过农杆菌介导的转化，利用转录后基因沉默技术研究了花椒的遗传转化。转化的植物在有或没有50 mm NaCl的情况下生长，并测量表达水平和生理参数。关键结果发现，50 mm NaCl诱导野生型（WT）植物根中ZxSOS 1转录物增加620%，但ZxHKT1; 1转录物仅增加80%。因此，ZxSOS 1转运Na（+）的能力超过ZxHKT1; 1，并且Na（+）通过ZxSOS 1被装载到木质部中并被递送到芽。然而，在ZxNHX沉默的系（L7）中，将Na（+）螯合到叶片液泡中的能力减弱，这反过来又调节了Na（+）从根到芽的长距离运输。在L7的根中，NaCl（50 mm）仅使ZxSOS 1的转录本增加10%，而ZxHKT 1; 1的转录本增加53%。因此，在L7中，ZxHKT1; 1对Na（+）的转运能力超过ZxSOS 1。Na（+）从木质部流中卸载，从而减少了Na（+）在叶片中的积累和相对分配，但增加了Na（+）在根中的相对分配和K（+）对Na（+）的净选择性运输能力。ZxNHX的沉默还引发了ZxAKT1和ZxSKOR在根中的下调，导致在50 mm NaCl中生长的植物中所有组织中K（+）积累的显著减少。这些变化导致渗透调节显著降低，从而抑制ZxNHX沉默株系的生长。结论ZxNHX通过反馈调节Na+、K+转运相关基因的表达，在全株水平上调控Na+、K+的吸收、长距离转运及其动态平衡。最终结果是保持了在Z中观察到的特征盐积累。花椒及其正常生长的调控。提出了ZxNHX在调控Z.在盐条件下的花椒。
BACKGROUND AND AIMS In order to cope with arid environments, the xerohalophyte Zygophyllum xanthoxylum efficiently compartmentalizes Na(+) into vacuoles, mediated by ZxNHX, and maintains stability of K(+) in its leaves. However, the function of ZxNHX in controlling Na(+) and K(+) homeostasis at the whole-plant level remains unclear. In this study, the role of ZxNHX in regulating the expression of genes involved in Na(+) and K(+) transport and spatial distribution was investigated. METHODS The role of ZxNHX in maintaining Na(+) and K(+) homeostasis in Z. xanthoxylum was studied using post-transcriptional gene silencing via Agrobacterium-mediated transformation. Transformed plants were grown with or without 50 mm NaCl, and expression levels and physiological parameters were measured. KEY RESULTS It was found that 50 mm NaCl induced a 620 % increase in transcripts of ZxSOS1 but only an 80 % increase in transcripts of ZxHKT1;1 in roots of wild-type (WT) plants. Consequently, the ability of ZxSOS1 to transport Na(+) exceeded that of ZxHKT1;1, and Na(+) was loaded into the xylem by ZxSOS1 and delivered to the shoots. However, in a ZxNHX-silenced line (L7), the capacity to sequester Na(+) into vacuoles of leaves was weakened, which in turn regulated long-distance Na(+) transport from roots to shoots. In roots of L7, NaCl (50 mm) increased transcripts of ZxSOS1 by only 10 %, whereas transcripts of ZxHKT1;1 increased by 53 %. Thus, in L7, the transport ability of ZxHKT1;1 for Na(+) outweighed that of ZxSOS1. Na(+) was unloaded from the xylem stream, consequently reducing Na(+) accumulation and relative distribution in leaves, but increasing the relative distribution of Na(+) in roots and the net selective transport capacity for K(+) over Na(+) from roots to shoots compared with the WT. Silencing of ZxNHX also triggered a downregulation of ZxAKT1 and ZxSKOR in roots, resulting in a significant decrease in K(+) accumulation in all the tissues in plants grown in 50 mm NaCl. These changes led to a significant reduction in osmotic adjustment, and thus an inhibition of growth in ZxNHX-silenced lines. CONCLUSIONS The results suggest that ZxNHX is essential for controlling Na(+), K(+) uptake, long-distance transport and their homeostasis at whole-plant level via feedback regulation of the expression of genes involved in Na(+), K(+) transport. The net result is the maintenance of the characteristic salt accumulation observed in Z. xanthoxylum and the regulation of its normal growth. A model is proposed for the role of ZxNHX in regulating the Na(+) transport system in Z. xanthoxylum under saline conditions.