Ammonium transporter 1 (AMT1) gene family in tomato (Solanum lycopersicum L.): Bioinformatics,physiological and expression analyses under drought and salt stresses

Nitrogen (N) is an essential macronutrient for plants, and mainly taken from the soil as ammonium (NH⁺⁴). It is particularly transported into the plants by AMmonium Transporters (AMTs), which are plasma membrane proteins. In the present study, genome-wide identification, physiological and expression analyses of tomato (Solanum lycopersicum L.) ammonium transporters 1 (SlAMT1) genes under drought and salt stresses were performed. Sequence analyses revealed the presence of variations in SlAMT1s at nucleotide and protein levels. While all the SlAMT1s comprise an ammonium transporter domain (PF00909), the numbers of their transmembrane helices were found to be diverse. Digital expression analyses proved that SlAMT1–3 gene had different expression patterns compared to the others, suggesting its functional diversities. The expression analyses revealed that SlAMT1 genes were 0.16 and 5.94 -fold down-regulated under drought and salt stresses, respectively. The results suggested that expression of SlAMT1 genes were adversely affected by abiotic stress conditions.     

The expression of a potato (Solanum tuberosum) S-RNase gene in Nicotiana tabacum pollen

Self-incompatibility in the Solanaceae is controlled by a single multiallelic genetic locus, the S locus. The stylar gene products of the S locus are abundant glycoproteins with ribonuclease activity, secreted in the transmitting tract tissue of the pistil. To investigate the structural and functional integrity and possible phenotypic effects of expression of the S-gene product in the male gametophyte, N. tabacum plants were transformed with a construct containing the genomic S ₂ -RNase coding sequence from S. tuberosum under the control of the promoter of the pollen-specific LAT52 gene from tomato. The expression pattern of the S ₂ RNase in the male gametophyte at both the protein and RNA level was found to be identical to that already reported for expression of the -glucuronidase (GUS) gene directed by the LAT52 promoter in transgenic tomato and tobacco. The S ₂ -RNase gene fusion led to a tissue-specific and developmentally regulated accumulation of the S ₂ polypeptide in pollen of transgenic tobacco plants. The transgenic protein product was of the same size and charge as the potato stylar product, had ribonuclease activity, and was glycosylated. The transgenic plants, however, did not show any morphological variations in their flower organs, and their fertility was not influenced by the accumulation of the S ₂ -RNase protein in pollen.     

cDNA cloning and expression of a potato (Solanum tuberosum) invertase

A cDNA clone encoding an invertase isoenzyme has been isolated from a potato leaf cDNA library. The deduced amino acid sequence shows significant similarities to previously characterised invertases. The highest degree of overall similarity, including the signal peptide sequence, is to carrot cell wall invertase, suggesting that the potato gene encodes an apoplastic enzyme. Expression of the gene, as determined by RT-PCR, is detected in stem and leaf tissue, and at lower levels in tuber, but is absent from roots.     

Drought and chlorophyll fluorescence in field-grown potato (Solanum tuberosum)

Light interception, stomatal conductance and chlorophyll fluorescence were measured in potato ( Solanum tuberosum L.) grown either irrigated, or droughted from the time of plant emergence. Compared with the irrigated treatment, drought reduced both light interception and stomatal conductance. In both treatments, the yields of variable fluorescence in the dark- and light-adapted states (F_y/F_m and F'_v/F'_m, respectively) were negatively correlated with photosynthetic photon flux density (PPFD) and mirrored daytime changes in PPFD. Photochemical quenching was positively correlated with PPFD, but the dominant effect of F'_v/F'_m resulted in a decrease in the quantum yield of photosystem II (PSII) electron transport with increasing PPFD.
Drought had no significant effect on the functioning of PSII and the balance between photochemical and non-photochemical quenching was unaffected. Non-photochemical quenching was not increased by drought and the quantum yield of PSII electron transport was unaffected. It is concluded that, in leaves of droughted plants, excess energy, resultant of stomatal limitation of photosynthesis, was dissipated by photochemical quenching such as increased photorespiration.     

马铃薯StZnT11的电子克隆、表达及生物信息学分析

马铃薯锌转运蛋白(Solanum tuberosum zinc transporter 11,StZnT11)对于维持细胞中锌稳态至关重要。通过研究StZnT11在非生物胁迫和生物胁迫下的表达情况,为验证马铃薯StZnT11在青枯菌生物胁迫过程中的作用奠定了基础。从前期工作获得的表达文库中得到EST序列,利用NCBI中的Blast工具,对原始序列进行同源性分析,选择与原始序列的相似度、覆盖度、e期望值最高的一条同源对象序列。通过电子克隆,得到StZnT11基因。采用生物信息学方法对StZnT11基因的基因序列及编码的氨基酸组成、理化性质、分子进化、磷酸化位点、高级结构等多角度进行分析。结果表明,该基因cDNA全长1300bp,编码348个氨基酸,编码蛋白含23个磷酸化位点,有1个信号肽,有9个跨膜区域,是定位在质膜上的疏水性蛋白。通过氨基酸序列比对,StZnT11蛋白与烟草、番茄和辣椒等植物中的锌转运蛋白同源性较高。实时荧光定量聚合酶链反应检测结果表明,StZnT11在不同浓度的外源植物激素脱落酸(ABA)的作用下上调。组织定位检测提示StZnT11主要表达于特定组织(茎维管系统的韧皮部和叶片维管束)。这些结果为进一步进行该基因的实验克隆及功能验证研究提供了理论依据。     

Temperature regulates tuber-inducing lipoxygenase-derived metabolites in potato (Solanum tuberosum)

Temperature is one of the major environmental factors affecting potato tuberization. It has been suggested that lipoxygenase (LOX) mediates between temperature and tuber induction. In this study, the contents of the LOX-derived metabolites hydroperoxylinolenic acid (HPOT), jasmonic acid (JA), tuberonic acid (TA) and tuberonic acid glucoside (TAG) were analyzed in leaves of potatoes growing at different temperatures. At low, tuber-inducing temperature, endogenous levels of JA, TA and TAG rise, indicating their crucial role in tuber induction. The concentration of 13(S)-HPOT seems not to be directly affected by temperature. Instead, the molecule has only a short half-life in leaves and is readily metabolized.     

Accumulation of vitamin E in potato (Solanum tuberosum) tubers

Vitamin E (tocopherol) is a powerful antioxidant essential for human health and synthesized only by photosynthetic organisms. The effects of over-expression of tocopherol biosynthetic enzymes have been studied in leaves and seeds, but not in a non-photosynthetic, below-ground plant organ. Genetic and molecular approaches were used to determine if increased levels of tocopherols can be accumulated in potato (Solanum tuberosum L.) tubers through metabolic engineering. Two transgenes were constitutively over-expressed in potato: Arabidopsis thaliana p-hydroxyphenylpyruvate dioxygenase (At-HPPD) and A. thaliana homogentisate phytyltransferase (At-HPT). α-Tocopherol levels in the transgenic plants were determined by high-performance liquid chromatography. In potato tubers, over-expression of At-HPPD resulted in a maximum 266% increase in α-tocopherol, and over-expression of At-HPT yielded a 106% increase. However, tubers from transgenic plants still accumulated approximately 10- and 100-fold less α-tocopherol than leaves or seeds, respectively. The results indicate that physiological and regulatory constraints may be the most limiting factors for tocopherol accumulation in potato tubers. Studying regulation and induction of tocopherol biosynthesis should reveal approaches to more effectively engineer crops with enhanced tocopherol content.     

Influence of salinity on axillary bud cultures of six lowland tropical varieties of potato (Solanum tuberosum)

Axillary bud cultures of six low-land tropical varieties of potato Solanum tuberosum (L. T. 2, 5, 6, 7, 8 and 9) were studied for their response to salinity stress using crude sea salt. Concentrations of 0.8% and above severely inhibited the growth, while decreased growth was observed between 0.4% and 0.6% salt in all the varieties, with occasional shoot tip necrosis and compound leaf formation. A lower concentration of salt (0.2%) was beneficial and increased shoot weight in most varieties. Protein content showed a positive correlation with proline levels, indicating that proline accumulation was due to new synthesis rather than breakdown of existing proteins. Soluble carbohydrates increased in the stem with increasing salt. Roots showed an increase in sodium content while shoots showed increased potassium levels, with increasing salt concentrations. There was a positive correlation between dry weight yields and K/Na ratio. It is apparent that the synthesis of proline, accumulation of soluble carbohydrates as well as increase in potassium and sodium content were all used to adjust the physiology in response to salt stress by the different varieties of potato, with varying degrees, in the present study.     

Biological containment of potato (Solanum tuberosum): outcrossing to the related wild species black nightshade (Solanum nigrum) and bittersweet (Solanum dulcamara)

The biological containment of the potato (Solanum tuberosum) was assessed by establishing the crossability of this tuberous crop with the related wild non-tuberous species in The Netherlands, black nightshade (S. nigrum) and bittersweet (S. dulcamara). To circumvent crossability barriers, genotypes with different ploidy number were employed and crosses were performed under different environmental conditions. S. dulcamara was shown to be incongruent with potato at all ploidy levels, while S. nigrum displayed unilateral incompatibility. If S. nigrum was emasculated and used as female, fertilization by potato pollen resulted in berry set and seed development. Emasculation of S. nigrum was essential in this cross, because analysis of the fertilization process demonstrated that this species is highly self-compatible and potato pollen was outcompeted by pollen of S. nigrum. The hybrid seeds derived from this cross did not mature and appeared not to be viable. By application of the technique of embryo rescue of immature embryos, hybrid plants could be obtained. However, these hybrid plants proved to be sterile. These data demonstrate that gene flow by pollen dispersal from potato to its most common wild relatives in Western Europe is highly unlikely. The potato is thus a naturally contained species in this part of the world.     

Expression of the IL-2 gene in the potato (Solanum tuberosum cv. Superior)

We intended to examine the expression of the T-cell growth factor (human interleukin-2) so that a binary vector, pSSK-1, carrying the IL-2 gene was constructed and transferred intoA. tumefaciens for the purpose of the transformation of the potato (Solanum tuberosum cv. Superior). All of theAgrobacterium-infected potato explants were regenerated to shoots in modified MS medium and 81% of them rooted on the medium containing kanamycin (200 mg/L). Southern and Northern analysis were performed to verify the transformation events. EL-ISA test indicated that IL-2 protein was produced from IL-2-transformed potatoes. These results suggested expression and production of the IL-2 protein from the transgenic potato.