渗透胁迫调节基因——Na^+/H^+ Antiporter基因与植物耐盐性

Na+/H+Antiporter基因与植物耐盐性密切相关,其编码产物Na+/H+逆向转运蛋白通过Na+外排和Na+区隔化来维持植物细胞内较低的Na+水平,降低Na+的毒害,从而对植物的耐盐性起重要作用。

Cloning and Identification of A New Na^+/H^+ Antiporter Gene ZmSOS1 in Maize(Zea mays L.)

[ Objective] The study aimed to clone and identify Na^＋/H^＋ antiporter genes in maize, and provided the information for characterizing the function of such genes in abiotic stress tolerance of maize. Method The in silico cloning, RT-PCR, and bioinformatics analysis were used in this study. Result By in sifico cloning, a plasma membrane Na^＋/H^＋ antiporter gene, named as ZmSOS1 （EMBL accession No. BN001309）, was cloned from maize （ Zea mays L. ）. ZmSOS1 has an open reading frame （ORF） of 3 411 bp which encoded a protein of 1 136 amino acids. By multiple sequence alignment analysis, it showed the predicated peptide of ZmSOS1 were 61% and 82% identities in amino acids to the plasma membrane Na^＋/H^＋ antiporter AtSOS1 and OsSOS1, respectively. The RT-PCR analysis revealed that ZmSOS1 could be significantly up-regulated by salt stress, which indicated ZmSOS1 might play a role in salt tolerance of maize. Conclusion ZmSOS1 is a putative plasma membrane Na^＋/H^＋ antiporter gene and may play a role in abiotic stress tolerance of maize.

Cloning and Characterization of the Na^+/H^+ Antiport Genes from Triticum aestivum

The Na+/H+ antiport genes namedTaNHX1andTaNHX2were cloned by screening a salt_stressed wheat cDNA library using rice Na+/H+ antiport cDNA fragment as the probe. Sequencing analysis showed thatTaNHX1was 2 029 bp in length and contained a complete ORF of 1 638 bp. TheTaNHX1encodes a polypeptide of 546 amino acids with a transmembrane domain DIFFIYLLPPI.TaNHX2was 1 693 bp in length consisting of a partial ORF followed by a 3′_UTR of 808 bp. The amino acid sequence of these two genes were about 70% identical to the known NHX genes from rice, Arabidopsis and Atriplex. A RT_PCR assay showed that the level ofTaNHX1transcripts was increased and reached a steady higher level in the seedlings after 3 h treatment with 400 mmol/L NaCl.

Dynamic changes of phosphatidylinositol and phosphatidylinositol 4-phosphate levels modulate H^(+)-ATPase and Na^(+)/H^(+) antiporter activities to maintain ion homeostasis in Arabidopsis under salt stress

Plant metabolites are dynamically modified and distributed in response to environmental changes.How-ever,it is poorly understood how metabolic change functions in plant stress responses.Maintaining ion ho-meostasis under salt stress requires coordinated activation of two types of central regulators:plasma membrane(PM)H^(+)-ATPase and Na^(+)/H^(+) antiporter.In this study,we used a bioassay-guided isolation approach to identify endogenous small molecules that affect PM H^(+)-ATPase and Na^(+)/H^(+) antiporter activities and identified phosphatidylinositol(PI),which inhibits PM H^(+)-ATPase activity under non-stress conditions in Arabidopsis by directly binding to the C terminus of the PM H^(+)-ATPase AHA2.Under salt stress,the phosphatidylinositol 4-phosphate-to-phosphatidylinositol(PI4P-to-PI)ratio increased,and PI4P bound and activated the PM Na^(+)/H^(+) antiporter.PI prefers binding to the inactive form of PM H^(+)-ATPase,while PI4P tends to bind to the active form of the Na^(+)/H^(+) antiporter.Consistent with this,pis1 mutants,with reduced levels of PI,displayed increased PM H^(+)-ATPase activity and salt stress toler-ance,while the pi4kβ1 mutant,with reduced levels of PI4P,displayed reduced PM Na^(+)/H^(+) antiporter activity and salt stress tolerance.Collectively,our results reveal that the dynamic change between PI and PI4P in response to salt stress in Arabidopsis is crucial for maintaining ion homeostasis to protect plants from un-favorable environmental conditions.

利用转基因技术创造甜菜耐盐新种质

采用农杆菌介导法将来源于E coli的胆碱脱氢酶 (CDH)基因 (betA)和来源于拟南芥的Na+ /H+antiport基因分别转入 5个糖甜菜品种的丛生芽细胞 ,获得了转基因植株。在耐盐性筛选中 ,转基因植株存活率高 ,部分植株生长较好 ,表现出比对照植株明显提高的耐盐性。在 2 %～ 3%NaCl胁迫下 ,少数转基因植株仍生长正常 ,显示出高耐盐性。本研究表明 ,转入在不同盐胁迫反应途径中起关键作用的酶基因均可提高甜菜耐盐性 。

Overexpression of the Suaeda salsa SsNHX1 gene confers enhanced salt and drought tolerance to transgenic Zea mays

Maize is one of the most important crops worldwide, but it suffers from salt stress when grown in saline-alkaline soil. There is therefore an urgent need to improve maize salt tolerance and crop yield. In this study, the SsNHX1 gene of Suaeda salsa, which encodes a vacuolar membrane Na~+/H~+ antiporter, was transformed into the maize inbred line 18-599 by Agrobacterium-mediated transformation. Transgenic maize plants overexpressing the SsNHX1 gene showed less growth retardation when treated with an increasing NaCl gradient of up to 1%, indicating enhanced salt tolerance. The improved salt tolerance of transgenic plants was also demonstrated by a significantly elevated seed germination rate(79%) and a reduction in seminal root length inhibition. Moreover, transgenic plants under salt stress exhibited less physiological damage. SsNHX1-overexpressing transgenic maize accumulated more Na~+ and K~+ than wild-type(WT) plants particularly in the leaves, resulting in a higher ratio of K~+/Na~+ in the leaves under salt stress. This result revealed that the improved salt tolerance of SsNHX1-overexpressing transgenic maize plants was likely attributed to SsNHX1-mediated localization of Na~+ to vacuoles and subsequent maintenance of the cytosolic ionic balance. In addition, SsNHX1 overexpression also improved the drought tolerance of the transgenic maize plants, as rehydrated transgenic plants were restored to normal growth while WT plants did not grow normally after dehydration treatment. Therefore, based on our engineering approach, SsNHX1 represents a promising candidate gene for improving the salt and drought tolerance of maize and other crops.

Introduction of AtNHX1 into beet improved salt-tolerance of transgenic plants

AtNHX1 gene encoding the Na ^＋/H ^＋ antiport on the vacuole membrane of Arabidopsis was transferred into small bud tips of 1-3mm in length derived from immature inflorescence cultures of six genotypes of beet （ Beta vulgaris L. ） by the infection of Agrobacterium tumefaciens and transgenic plants with improved salt-tolerance were obtained. When transgenic plants at 5-leaf stage were potted in sand and irrigated with solutions containing a range of concentrations of NaCl （171-513mM）, they showed minor symptoms of damage from salinity and better tolerance than the controls. There were considerable discrepancies of salt-tolerance between transgenic plants originated from the same genotype and also between different genotypes. After vernalization, bolting transgenic plants were enveloped with two layers of gauzes for self-pollination. T1 seedlings tolerant to 342-427mM NaCl were obtained respectively. These results revealed that it was feasible to improve salt-tolerance of beets by the introduction of AtNHX1 gene into cultured bud cells.