Xiaohua Long

Salt Stress Encourages Proline Accumulation by Regulating Proline Biosynthesis and Degradation in Jerusalem Artichoke Plantlets

Proline accumulation is an important mechanism for osmotic regulation under salt stress. In this study, we evaluated proline accumulation profiles in roots, stems and leaves of Jerusalem artichoke (Helianthus tuberosus L.) plantlets under NaCl stress. We also examined HtP5CS, HtOAT and HtPDH enzyme activities and gene expression patterns of putative HtP5CS1, HtP5CS2, HtOAT, HtPDH1, and HtPDH2 genes. The objective of our study was to characterize the proline regulation mechanisms of Jerusalem artichoke, a moderately salt tolerant species, under NaCl stress. Jerusalem artichoke plantlets were observed to accumulate proline in roots, stems and leaves during salt stress. HtP5CS enzyme activities were increased under NaCl stress, while HtOAT and HtPDH activities generally repressed. Transcript levels of HtP5CS2 increased while transcript levels of HtOAT, HtPDH1 and HtPDH2 generally decreased in response to NaCl stress. Our results supports that for Jerusalem artichoke, proline synthesis under salt stress is mainly through the Glu pathway, and HtP5CS2 is predominant in this process while HtOAT plays a less important role. Both HtPDH genes may function in proline degradation.

Cadmium Accumulation and Translocation in Two Jerusalem Artichoke (Helianthus tuberosus L.) Cultivars

Abstract Jerusalem artichoke (Helianthus tuberosus L.) not just can be used for bioethanol production but may be potentially used in phytoremediation for the removal of heavy metal pollutants. Two Jerusalem artichoke cultivars, N2 and N5, were subjected to six cadmium (Cd) concentrations (0, 5, 25, 50, 100 and 200 mg L−1) to investigate Cd tolerance and accumulation. After 21 days of growth, the effects of Cd on growth, chlorophyll content, net photosynthetic rate, intercellular CO2 concentration and malondialdehyde content were evaluated. Most growth parameters were reduced under Cd stress. The two Jerusalem artichoke cultivars had relatively high Cd tolerance and accumulation capacity (> 100 mg kg−1), with N5 being more tolerant and having higher Cd accumulation than N2. Roots accumulate more Cd than stems and leaves. The bioconcentration factors (far higher than 1) and translocation factors (lower than 1) decreased with an increase in Cd applied. The results suggested that Jerusalem artichoke could be grown at relatively high Cd loads, and N5 could be an excellent candidate for phytoremediation of Cd-contaminated soils.

Cloning of exoinulinase gene from Penicillium janthinellum strain B01 and its high-level expression in Pichia pastoris

Aims:  The aim of this study is to improve exoinulinase production by expression of a cloned exoinulinase gene inuA1 (GenBank accession no. JF961344) from Penicillium janthinellum strain B01 in Pichia pastoris.

Salinity altered root distribution and increased diversity of bacterial communities in the rhizosphere soil of Jerusalem artichoke

The interaction between roots and bacterial communities in halophytic species is poorly understood. Here, we used Jerusalem artichoke cultivar Nanyu 1 (NY-1) to characterise root distribution patterns and determine diversity and abundance of bacteria in the rhizosphere soil under variable salinity. Root growth was not inhibited within the salinity range 1.2 to 1.9 g salt/kg, but roots were mainly confined to 0–20 cm soil layer vertically and 0–30 cm horizontally from the plant centre. Root concentrations of K+, Na+, Mg2+ and particularly Ca2+ were relatively high under salinity stress. High salinity stress decreased soil invertase and catalase activity. Using a next-generation, Illumina-based sequencing approach, we determined higher diversity of bacteria in the rhizosphere soil at high than low salinity. More than 15,500 valid reads were obtained, and Proteobacteria, Acidobacteria, Bacteroidetes and Actinobacteria predominated in all samples, accounting for >80% of the reads. On a genus level, 636 genera were common to the low and high salinity treatments at 0–5 cm and 5–10 cm depth. The abundance of Steroidobacter and Sphingomonas was significantly decreased by increasing salinity. Higher Shannon and Chao 1 indices with increasing severity of salt stress indicated that high salt stress increased diversity in the bacterial communities.

Influence of nitrogen fertilization on diazotrophic communities in the rhizosphere of the Jerusalem artichoke (Helianthus tuberosus L.).

Diazotrophs in the soil may be influenced by plant factors as well as nitrogen (N) fertilization. In this study, we investigated potential diazotrophic communities in the rhizosphere of the Jerusalem artichoke (Helianthus tuberosus L.) supplied with differing amounts of N. The community structure of N(2)-fixing bacteria was profiled using the length heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphism (T-RFLP) based on a variation in the nifH gene. Higher numbers of diazotrophs were detected by T-RFLP compared to LH-PCR. The lowest number of N(2)-fixing bacteria was observed in the rhizosphere soil with high N fertilization. T-RFLP was a better method than LH-PCR for profiling microbial diversity of diazotrophs using multidimensional scaling (MDS) and analysis of similarity (ANOSIM) of fingerprints as well as diversity measures. The supply of N fertilizer appeared to negatively influence the abundance of diazotrophs in the rhizophere of the Jerusalem artichoke.

Colonization by endophytic Ochrobactrum anthropi Mn1 promotes growth of Jerusalem artichoke

The Ochrobactrum anthropi Mn1 strain, taxonomically identified using 16S ribosomal DNA sequence, was isolated from roots of Jerusalem artichoke. Its endophytic colonization was investigated microscopically using green fluorescent protein introduced by vector pHC60. The strain entered Jerusalem artichoke tissues through the root, and was localized in the roots and stems. The plant growth‐promoting (PGP) effects of O. anthropi Mn1 were assessed in greenhouse as well as field trials with different nitrogen supplies. Only under moderate to ample nitrogen supply, could O. anthropi Mn1 promoted growth of host plant. The PGP effects of the strain were symbiotic nitrogen fixation, root morphological optimization and enhanced nutrient uptake. We hypothesize that the symbiotic interspecies interaction might be quorum sensing related.

Response of Two Jerusalem Artichoke (Helianthus tuberosus) Cultivars Differing in Tolerance to Salt Treatment

Abstract To explore genetic variability for two Jerusalem artichoke ( Helianthus tuberosus ) cultivars, N1 (the sixth-generation cultivated with 75% seawater irrigation for six years) and N7 (a general variety), a experiment was conducted to study the changes in physiological attributes under different concentrations (0%, 10% and 25% of seawater concentration in greenhouse and 0%, 30% and 50% of seawater concentration in the field) of seawater salinity stress. In the greenhouse experiment, decreases of dry growth rate, but increases of dry matter percentage and membrane injury occurred in both the genotypes at 10% and 25% seawater treatments, although lesser cell membrane damage was observed in N1 than N7. N1 accumulated greater contents of Na + , Cl − , soluble sugar and proline in leaves compared with N7. In the field experiment, the yields of shoot, root and tuber, and the contents of total-sugar and inulin in tubers of N1 were higher than those of N7. Lesser degree of salt injury in N1 indicated that the relatively salt-tolerant cultivar had higher K + /Na + ratio, lower Na + /Ca 2+ ratio, and the salt-induced enhancement of osmotic adjustment.

Developing and sustainably utilize the coastal mudflat areas in China.

Coastal mudflat areas are regarded as the important reserve land resource in China. Rational exploitation and development of the mudflat areas can relieve the stress of inadequate land resources. Probing into the developing models of resource exploitation of coastal tidal mudflats is one of the important components of achieving the sustainable development in the coastal areas. Therefore, the development history of coastal mudflats after 1950s in China is briefly introduced in this paper. Then, the status in quo of the modes of development and utilization of coastal mudflat in China the paper is reviewed with a special attention payed to the agricultural use of coastal resource, especially halophytes and improved salt-tolerant varieties planting, agricultural dyke pond and coastal saline-alkali soil remediation. Based on related research frontier, sustainable developmental prospects of these coastal areas are presented as well.

Analysis of phenolic acids of Jerusalem artichoke (Helianthus tuberosus L.) responding to salt-stress by liquid chromatography/tandem mass spectrometry.

Plant phenolics can have applications in pharmaceutical and other industries. To identify and quantify the phenolic compounds in Helianthus tuberosus leaves, qualitative analysis was performed by a reversed phase high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) and quantitative analysis by HPLC. Ten chlorogenic acids (CGAs) were identified (3-o-caffeoylquinic acid, two isomers of caffeoylquinic acid, caffeic acid, p-coumaroyl-quinic acid, feruloylquinic acid, 3,4-dicaffeoyquinic acid, 3,5-dicaffeoylquinic acid, 1,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid) by comparing their retention times, UV-Vis absorption spectra, and MS/MS spectra with standards. In addition, four other phenolic compounds, including caffeoyl glucopyranose, isorhamnetin glucoside, kaempferol glucuronide, and kaempferol-3-o-glucoside, were tentatively identified in Helianthus tuberosus leaves for the first time. The 3-o-caffeoylquinic acid (7.752 mg/g DW), 4,5-dicaffeoylquinic acid (5.633 mg/g DW), and 3,5-dicaffeoylquinic acid (4.900 mg/g DW) were the major phenolic compounds in leaves of Helianthus tuberosus cultivar NanYu in maturity. The variations in phenolic concentrations and proportions in Helianthus tuberosus leaves were influenced by genotype and plant growth stage. Cultivar NanYu had the highest concentration of phenolic compounds, in particular 3-o-caffeoylquinic acid and 4,5-dicaffeoylquinic acid compared with the other genotypes (wild accession and QingYu). Considering various growth stages, the concentration of total phenolics in cultivar NanYu was higher at flowering stage (5.270 mg/g DW) than at budding and tuber swelling stages. Cultivar NanYu of Helianthus tuberosus is a potential source of natural phenolics that may play an important role in the development of pharmaceuticals.

Balance between salt stress and endogenous hormones influence dry matter accumulation in Jerusalem artichoke

Salinity is one of the most serious environmental stresses limiting agricultural production. Production of Jerusalem artichoke on saline land is strategically important for using saline land resources. The interaction between plant hormones and salinity stress in governing Jerusalem artichoke (Helianthus tuberosus) growth is unclear. Jerusalem artichoke (variety Nanyu-1) was grown under variable salinity stress in the field, and a role of endogenous hormones [zeatin (ZT), auxins (IAA), gibberellins (GA3) and abscisic acid (ABA)] in regulating sugar and dry matter accumulation in tubers was characterized. Under mild salt stress (≤2.2gNaClkg(-1) soil), Nanyu-1 grew well with no significant alteration of dry matter distribution to stems and tubers. In contrast, under moderate salt stress (2.7gNaClkg(-1) soil), the distribution to stem decreased and to tubers decreased significantly. Mild salt stress induced sugar accumulation in tubers at the beginning of the tuber-expansion period, but significantly inhibited (i) transfer of non-reducing sugars to tubers, and (ii) polymerization and accumulation of fructan during the tuber-expansion stage. Under different salinity stress, before the stolon growth, the ratio of IAA/ABA in leaves increased significantly and that of GA3/ABA increased slightly; during tuber development, these ratios continued to decrease and reached the minimum late in the tuber-expansion period. While, salt stress inhibited (i) underground dry matter accumulation, (ii) tuber dry matter accumulation efficiency, (iii) transport of non-reducing sugars to tubers, and (iv) fructan accumulation efficiency during the tuber-expansion period; these effects were accompanied by significantly decreased tuber yield with an increase in salinity. With soil salinity increasing, the synthesis of IAA and GA3 was inhibited in leaves and tubers, while ABA synthesis was stimulated. In brief, tuber yield would significantly decreased with the increase of salinity.