Variation of Kukoamine A (KuA) and B (KuB) contents and related meteorological factors for Cortex Lycii radicis of different areas

Kukoamines are polyamine alkaloids present in Cortex Lycii (LyC), which is the root bark of Lycium chinense Mill. or L. barbarum L. Environmental conditions and geographical distribution influence the biosynthesis and accumulation of Kukoamines in Lycium species, thus directly affecting the quality of LyC. To identify the factors that influence Kukoamine A (KuA) and Kukoamine B (KuB) accumulation, the KuA and KuB contents of L. chinense and L. barbarum LyC collected from different areas or potted L. barbarum LyC with soil collected from different areas were measured, and the correlation of Kukoamine contents with meteorological factors and soil constituents were analyzed. In both L. barbarum and L. chinense, the KuA and KuB contents of LyC planted in Zhongning were significantly higher than those of LyC planted in other areas. Three L. barbarum species planted in soil collected from different areas presented significant difference in the KuA and KuB content of LyC. The contents of both KuA and KuB showed negative correlation with annual precipitation, mean temperature, and mean humidity, while positively correlated with soil pH, altitude, mean diurnal temperature difference, and annual sunshine hours, but there was no significant correlation with any soil compositions. It might be illustrated that soil pH and meteorological factors are important aspects affecting the quality of LyC.     

Growth performance and physiological response in the halophyte Lycium barbarum grown at salt-affected soil

As a traditional Chinese medicinal plant, Lyciumbarbarum is of high economic value and has attracted many considerable interests in recent years. The plant is a perennial halophyte grown under extreme conditions, especially under highly saline soil. A pot experiment was carried out to quantify the responses of L. barbarum plants to soil salinity applied at 100 and 200 mM NaCl. The results demonstrate that 100 mM NaCl soil improves the growth of L. barbarum seedlings. Because the 100 mM NaCl soil enhanced plant height and dry matter by 20% and 30% compared with the nonsalinised soil, it is considered suitable, and the 200 mM NaCl soil showed negative effects, too extreme for the growth of L. barbarum. The leaf cations and betaine content increased significantly under salt stress. The leaf chlorophyll, gas exchange, photochemical efficiency, leaf area and soluble sugar contents showed a significant decrease under 200 mM NaCl stress compared with the nonsalinised and the 100 mM NaCl‐affected soil. The results do not provide a basic mechanism for the observed growth stimulation; however, they suggest that L. barbarum may be an economic species for cultivation in moderately saline areas such as northwest China.     

Investigation of Chinese Wolfberry (<Emphasis Type="Italic">Lycium</Emphasis> spp.) Germplasm by Restriction Site-Associated DNA Sequencing (RAD-seq)

Chinese wolfberry (Lycium spp.) is an important edible and medicinal plant, with a long cultivation history. The genetic relationships among wild Lycium species and landraces have been unclear for a number of reasons, which has hindered the breeding of modern Chinese wolfberry cultivars. In this study, we collected 19 accessions of Chinese wolfberry germplasm, and constructed the genetic relationship based on RAD-seq markers. We obtained 30.32 Gb of clean data, with the average value of each sample being 1.596 Gb. The average mapping rate was 85.7%, and the average coverage depth was 6.76 X. The phylogeny results distinguished all accessions clearly. All the studied landraces shared their most recent common ancestor with L. barbarum, which indicated that L. barbarum may be involved in cultivation of these landraces. The relationship of some landraces, namely the ‘Ningqi’ series, ‘Qingqi-1’ and ‘Mengqi-1,’ has been supported by the phylogeny results, while the triploid wolfberry was shown to be based on a hybrid between ‘Ningqi-1’ and a tetraploid wolfberry. This study uncovered the genetic background of Chinese wolfberry, and developed the foundation for species classification, accession identification and protection, and the production of hybrid cultivars of wolfberry.     

Class 1 non-symbiotic and class 3 truncated hemoglobin-like genes are differentially expressed in stone fruit rootstocks (Prunus L.) with different degrees of tolerance to root hypoxia

Root hypoxia produced by flooding or over-irrigation limits stone fruit tree development, particularly in orchards established on soils with restricted drainage. To overcome this problem, stone fruit trees are usually grafted on rootstocks (species or hybrid of the Prunus L. genus) with different degrees of tolerance to root hypoxia. However, the molecular base of such variability is largely unknown. In Arabidopsis thaliana (Heynh.), as well as in a number of crops and tree species, hemoglobin (Hb)-like genes stand out among hypoxia-related genes, but no such studies have been done with the Prunus species used as rootstocks. In this study, we analyzed the expression pattern of class 1 non-symbiotic Hb-like (nsHb) and class 3 truncated Hb-like (trHb) genes in Prunus rootstock roots with different responses to this stress. We observed that the putative Prunus nsHb and trHb genes were induced by root hypoxia in all analyzed Prunus genotypes, independently of their tolerance to hypoxia. However, Prunus nsHb and trHb genes had higher expression levels in roots of tolerant rootstocks. Prunus nsHb and trHb genes were also regulated by other abiotic stresses, such as salt stress and low temperatures. Our results suggest that changes in nsHb and trHb expressions could be part of the adaptive mechanisms that have evolved in the Prunus species to survive under hypoxia or other types of environmental stress that commonly challenge stone fruit tree orchards.     

Transgenic banana plants overexpressing a native plasma membrane aquaporin MusaPIP1;2 display high tolerance levels to different abiotic stresses

Water transport across cellular membranes is regulated by a family of water channel proteins known as aquaporins (AQPs). As most abiotic stresses like suboptimal temperatures, drought or salinity result in cellular dehydration, it is imperative to study the cause–effect relationship between AQPs and the cellular consequences of abiotic stress stimuli. Although plant cells have a high isoform diversity of AQPs, the individual and integrated roles of individual AQPs in optimal and suboptimal physiological conditions remain unclear. Herein, we have identified a plasma membrane intrinsic protein gene (MusaPIP1;2) from banana and characterized it by overexpression in transgenic banana plants. Cellular localization assay performed using MusaPIP1;2::GFP fusion protein indicated that MusaPIP1;2 translocated to plasma membrane in transformed banana cells. Transgenic banana plants overexpressing MusaPIP1;2 constitutively displayed better abiotic stress survival characteristics. The transgenic lines had lower malondialdehyde levels, elevated proline and relative water content and higher photosynthetic efficiency as compared to equivalent controls under different abiotic stress conditions. Greenhouse‐maintained hardened transgenic plants showed faster recovery towards normal growth and development after cessation of abiotic stress stimuli, thereby underlining the importance of these plants in actual environmental conditions wherein the stress stimuli is often transient but severe. Further, transgenic plants where the overexpression of MusaPIP1;2 was made conditional by tagging it with a stress‐inducible native dehydrin promoter also showed similar stress tolerance characteristics in in vitro and in vivo assays. Plants developed in this study could potentially enable banana cultivation in areas where adverse environmental conditions hitherto preclude commercial banana cultivation.     

Molecular Cloning and Expression Analysis of Nine ThTrx Genes in Tamarix hispida

Thioredoxins are small conserved proteins that play key roles in the oxidative stress response. In this study, nine Trx genes, including five Trxhs, three Trxms, and one Trx-like gene, were cloned from Tamarix hispida. The roles of these ThTrx genes were investigated under various abiotic stress conditions. Expression profiles of the nine ThTrx genes in response to different abiotic stresses in leaf and root tissues were constructed using quantitative real time-polymerase chain reaction. Differential expression of all nine ThTrx genes was observed (>2-fold) in response to NaCl, PEG, or CdCl₂ stress in at least one tissue, indicating that all of these genes act in abiotic stress responses. All ThTrx genes were induced (>2-fold) by abscisic acid (ABA) treatment in the leaves and especially in the roots, suggesting that ABA-dependent signaling pathways regulate ThTrxs. These results demonstrate that ThTrx expression constitutes an adaptive response to abiotic stress in T. hispida and plays an important role in abiotic stress tolerance.     

Comparative phylogenetic analysis of aquaporins provides insight into the gene family expansion and evolution in plants and their role in drought tolerant and susceptible chickpea cultivars

Aquaporins (AQPs) are water channel proteins that play a significant role in drought stress. Although the AQPs identified in multiple plant species, there is no detailed evolutionary and comparative study of AQPs regarding chickpea plant. The current study involved evolutionary analyses coupled with promoter and expression analyses of chickpea AQPs (CaAQPs). A total of 924 non-redundant AQPs were studied in 24 plant species including algae, mosses, lycophytes, monocots and dicots. Phylogenetic analysis demonstrated a clear divergence of eight AQP subfamilies (LIPs, SIPs, GIPs, NIPs, XIPs, PIPs, HIPs and TIPs). The comparative phylogenetic trees of AQP subfamilies among Arabidopsis, soybean, common bean, maize and chickpea demonstrated that the AQPs were highly species-specific. Interestingly, the dual NPA motif was conserved in all species. However, the ar/R selectivity filter signatures [W/T/S/N/G/A]-[V/S/L/I/A]-[S/G/A]-R (in NIPs), F-H-T-R (in PIPs), [H/N/Q/S]-[A/I/L/S/V]-[A/G]-[A/C/L/M/R/V] (in TIPs) and [V/I/L/M]-[V/I/A/F/M]-[A/S/F/C]-[N/F/L/I/A/S (in SIPs) were found in five species. Moreover, the Froger's positions (P1-P5) were found as [F/L/Y]-[S/T]-A-Y-[L/I/M/V/F] (in NIPs), [Q/E/M]-S-A-F-W (in PIPs), [A/L/S/T/V]-[A/C/N/S/T/V]-[P/R/S]-[Y/N/F]-[W/Q] (in TIPs) and [I/M/F]-[A/V]-[A/V]-Y-W (in SIPs). The MEME motif analyses showed that most of the motifs were specific to subfamily and subgroups. Tissue-specific expression profiling of CaAQPs revealed that CaTIPs and CaPIPs are highly expressed in most of the tissues, while CaNIPs and CaSIPs have low expression. In promoter analysis of CaAQPs, multiple stress-related cis-acting elements e.g. MYB, MYC, ABRE, etc. were found. Semi-quantitative RT-PCR analysis showed that CaPIP2;3 and CaNIP3;1 are positive regulator, while CaSIP1;1 and CaPIP2;1 have a negative role in drought tolerance. The findings and implications of this study are discussed in detail.     

Functional Exploration of Chaperonin (HSP60/10) Family Genes and their Abiotic Stress-induced Expression Patterns in Sorghum bicolor

Background Sorghum, the C4 dry-land cereal, important for food, fodder, feed and fuel, is a model crop for abiotic stress tolerance with smaller genome size, genetic diversity, and bio-energy traits. The heat shock proteins/chaperonin 60s (HSP60/Cpn60s) assist the plastid proteins, and participate in the folding and aggregation of proteins. However, the functions of HSP60s in abiotic stress tolerance in Sorghum remain unclear.MethodsGenome-wide screening and in silico characterization of SbHSP60s were carried out along with tissue and stress-specific expression analysis.ResultsA total of 36 HSP60 genes were identified in Sorghum bicolor. They were subdivided into 2 groups, the HSP60 and HSP10 co-chaperonins encoded by 30 and 6 genes, respectively. The genes are distributed on all the chromosomes, chromosome 1 being the hot spot with 9 genes. All the HSP60s were found hydrophilic and highly unstable. The HSP60 genes showed a large number of introns, the majority of them with more than 10. Among the 12 paralogs, only 1 was tandem and the remaining 11 segmental, indicating their role in the expansion of SbHSP60s. Majority of the SbHSP60 genes expressed uniformly in leaf while a moderate expression was observed in the root tissues, with the highest expression displayed by SbHSP60-1. From expression analysis, SbHSP60-3 for drought, SbHSP60-9 for salt, SbHSP60-9 and 24 for heat and SbHSP60-3, 9 and SbHSP10-2 have been found implicated for cold stress tolerance and appeared as the key regulatory genes.ConclusionThis work paves the way for the utilization of chaperonin family genes for achieving abiotic stress tolerance in plants.     

The Relationship between the Expression of Ethylene-Related Genes and Papaya Fruit Ripening Disorder Caused by Chilling Injury

Papaya (Carica papaya L.) is sensitive to low temperature and easy to be subjected to chilling injury, which causes fruit ripening disorder. This study aimed to investigate the relationship between the expression of genes related to ethylene and fruit ripening disorder caused by chilling injury. Papaya fruits were firstly stored at 7°C and 12°C for 25 and 30 days, respectively, then treated with exogenous ethylene and followed by ripening at 25°C for 5 days. Chilling injury symptoms such as pulp water soaking were observed in fruit stored at 7°C on 20 days, whereas the coloration and softening were completely blocked after 25 days, Large differences in the changes in the expression levels of twenty two genes involved in ethylene were seen during 7°C-storage with chilling injury. Those genes with altered expression could be divided into three groups: the group of genes that were up-regulated, including ACS1/2/3, EIN2, EIN3s/EIL1, CTR1/2/3, and ERF1/3/4; the group of genes that were down-regulated, including ACO3, ETR1, CTR4, EBF2, and ERF2; and the group of genes that were un-regulated, including ACO1/2, ERS, and EBF1. The results also showed that pulp firmness had a significantly positive correlation with the expression of ACS2, ACO1, CTR1/4, EIN3a/b, and EBF1/2 in fruit without chilling injury. This positive correlation was changed to negative one in fruit after storage at 7°C for 25 days with chilling injury. The coloring index displayed significantly negative correlations with the expression levels of ACS2, ACO1/2, CTR4, EIN3a/b, ERF3 in fruit without chilling injury, but these correlations were changed into the positive ones in fruit after storage at 7°C for 25 days with chilling injury. All together, these results indicate that these genes may play important roles in the abnormal softening and coloration with chilling injury in papaya.