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This study selected Dendrobium officinale protocorms as the experimental material and used different light-quality treatments and calcium signalling inhibitors to explore the mechanism of the biological response of calcium to light quality. The results indicate that a 1:3 red:blue (R:B) light ratio promotes the accumulation of biomass and polysaccharides in the protocorm. Nevertheless, this effect can be entirely counteracted by calmodulin (CaM) inhibitors and calcium ion-chelating agents. The possible mechanisms of this effect are as follows: (1) The Ca2+-CaM signal-regulated photosynthetic apparatus is improved by the R:B 1:3 light, increasing the CaM content and Ca2+-ATPase activity. Thus, R:B 1:3 light increases the development of the photosynthetic apparatus in the D. officinale protocorm, enhances its photosynthetic productivity, and promotes the activities of sucrose phosphatase; accordingly, biomass and sucrose accumulation increase. (2) R:B 1:3 light enhances Ca2+-CaM signalling and regulates glycometabolic processes to promote the activities of sucrose synthase, thus increasing fructose and glucose levels and providing sufficient synthetic precursors to promote polysaccharide production.

Dwarf bamboo Sasa argenteostriata (Regel) E.G. Camus has previously been considered as potential plant for metal phytoremediation. However, the dynamic responses and correlations among physiological resistances to high-concentration Pb exposure have not been described to date. This study conducted four Pb treatments (0, 1500, 3000, and 4500 mg kg–1) to examine the physiological resistance responses at days 7, 14, and 21. The findings showed that S. argenteostriata can regulate both the enzymatic system and the nonenzymatic system to synergistically overcome Pb damage. In addition, a significant positive correlation was found between enzymes and nonenzymatic substances, which were particularly apparent with regard to the superoxide dismutase (SOD) activities with phytochelatins (PCs) levels, peroxidase (POD), and glutathione reductase (GR) activities with glutathione (GSH) levels, as well as catalase (CAT) and ascorbate peroxidase (APX) activities with soluble protein (SP) levels. Furthermore, Pb concentration was the main factor that induced the physiological responses of S. argenteostriata to Pb stress. The antioxidant enzyme system and the AsA–GSH cycle were dominant resistance mechanisms under 1500 mg kg–1 Pb. AsA–GSH cycle and plant cell chelation were dominant resistance mechanisms under 3000 mg kg–1 Pb. Antioxidant enzymes and plant cell chelation were dominant resistance mechanisms under 4500 mg kg–1 Pb. This study provides comprehensive evidence regarding how both enzymatic and nonenzymatic systems of S. argenteostriata cooperate to alleviate the high-concentration soil Pb stress. The results highlight the environmental remediation potential of this species for Pb-contaminated media.

Cadmium (Cd) and zinc (Zn) coexist in the environment but interact differently in plants. Cosmos bipinnatus has been potentially considered as a Cd-accumulator. Thus, this study investigated the detoxification mechanism in C. bipinnatus seedlings under Cd, Zn and Cd + Zn stresses. In the present study, the presence of Zn inhibited Cd uptake and translocation, whereas Cd merely hindered Zn uptake. The concentration of Cd in soluble fraction significantly decreased and Cd was bounded to the cell wall in root under Cd + Zn stress. Meanwhile, Zn and Cd mutually decreased their concentrations in the ethanol extractable form (FE) and water extractable form (FW) in roots and shoots. Furthermore, Cd + Zn stress enhanced the activities of superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) compared to Cd stress alone. These results suggested that Zn effectively decreased Cd uptake and translocation, changed their subcellular distributions, regulated their chemical forms composition and increased antioxidative enzyme activities, thereby enhancing the tolerance to Cd in C. bipinnatus. This study physiologically revealed the interactive effect of Cd and Zn on the detoxification mechanism of Cd in C. bipinnatus and provided new information on phytoremediation of the heavy metal contaminated soils.

The significant influence of •NO on the stress response is well established; however, the precise metabolic pathways of •NO and RNS under metal stresses remain unclear. Here, the key components of ROS and RNS metabolism under Cd stress were investigated with multi-level approaches using high-quality forage white clover (Trifolium repens L.) plants. For the studied plants, Cd disturbed the redox homeostasis, affected the absorption of minerals, and exacerbated the degree of lipid peroxidation, thus triggering oxidative stress. However, •NO was also involved in regulating mineral absorption, ROS-scavenger levels and mRNA expression in Cd-treated white clover plants. In addition, GSNOR activity was up-regulated by Cd with the simultaneous depletion of •NO generation and GSNO but was counteracted by the •NO donor sodium nitroprusside. Response to Cd-stressed SNOs was involved in generating ONOO- and NO2-Tyr in accordance with the regulation of •NO-mediated post-translational modifications in the ASC-GSH cycle, selected amino acids and NADPH-generating dehydrogenases, thereby provoking nitrosative stress. Taken together, our data provide comprehensive metabolite evidence that clearly confirms the relationships between ROS and RNS in Cd-stressed plants, supporting their regulatory roles in response to nitro-oxidative stress and providing an in-depth understanding of the interaction between two families subjected to metal stresses.

Lilium sargentiae E.H. Wilson (Liliaceae) is an ornamental and economic flowering bulb in China. Unfortunately, due to low natural bulb multiplication rates or long juvenile phases, commercial release of a new genotype may take 10 or even 20 years. In this study, bulbs were expanded in test tubes by adding sucrose, to shorten the duration of the commercial production cycle. Results indicated that when sucrose, with a concentration of 60 g l−1, was supplied to the culture medium, the bulblets could be most effectively induced and expanded. The effect of sucrose on the formation and expansion of L. sargentiae was obvious and dominant. It was not connected to the osmotic potential of sucrose, nor entirely explained by the function of sucrose as an energy and carbon source. We used sugar analogues in the culturing of explanted materials to research the effect of sucrose-specific signaling on bulblet formation and expansion. Results showed that exogenous 3-O-methyl glucose could not induce and expand test-tube bulblets, which was similar to mannose, whereas isomaltulose could generate similar results to those obtained with sucrose. The results further indicated that the specific signalling of sucrose could be responsible for the effect on bulblets formation and swelling. We used the exclusion method to confirm above results and hypothesis, and observed that only a small part of sucrose was transformed by cell wall invertase and entered the cells through hexose transporters, playing a certain effect on bulbelt growth and development through hexose or hexose signaling systems. Overall, the effect of sucrose on bulblet induction and swelling could be explained by sucrose-specific signaling. Furthermore, this effect has a direct correlation with the sucrose-specific vector.

Phylogenetic relationships among the six Iris subgenera were reconstructed by chloroplast trnL-F sequences data using maximum likelihood. The entire matrix of aligned bases analyzed includes 1043 characters and the length of all sequences varied from 747 bp to 893 bp, and mutation sites accounted for 18.79% of the total length. The cluster analysis results accorded well with the subgeneric classification of Chinese Iris species. Results suggested rhizomes and sepals lacking ornament are ancestral characters, and subg. Xyridion and subg. Limniris are more primordial than another four subgenera. Subgenus Nepalensis and subg. Xyridion were resolved as monophyletic.

Fargesia Franchet emend. Yi is closely allied with Thamnocalamus Munro but differs in many major morphological characteristics. Based on traditional morphological characters, it is difficult to differentiate these two genera. The current study measured 19 species in these two genera to determine whether variations in 12 categories of major characters are continuous. In addition, a self-organizing map (SOM) and cluster analysis were used together to reveal whether the known species of Fargesia represent discontinuous sampling of Thamnocalamus. The results show that 46 morphological characteristics exhibited high variation at the generic and species levels. In addition, the cluster analysis showed that 32 morphological characteristics of Thamnocalamus and Fargesia were divided between two species and well separated from the outgroup. Additionally, significant differences (P Fargesia is not a result of discontinuous sampling of Thamnocalamus; thus, Fargesia should not be treated as a synonym for Thamnocalamus.

Cadmium (Cd) is a non-essential metallic element with potentially deleterious effects on plants, animals, and human health. Many studies have indicated that nitrogen (N) application can effectively alleviate Cd toxicity in plants. However, the function of nitrogen in this process remains unclear. In this study, high-throughput RNA sequencing and comparative analysis were carried out on poplar (Populus cathayana Rehd) trees treated with only Cd or co-treated with N and Cd, and both treatments were compared against a negative control (no Cd or N) and plants treated with only N. The results showed that approximately 48045828, 46712688, 46681202, and 48076990 clean reads were obtained in the control, Cd, N + Cd, and N treatments. Gene ontology and pathway enrichment analysis (KEGG) indicated that differentially expressed genes (DEGs) could be classified primarily into 144 pathways, among which 19 were related to heavy metal transportation and cell detoxification. The up- and down-regulated DEGs were predominately involved in glutathione (GSH) synthesis, cysteine (Cys), glycine (Gly), brassinosteroid (BR), and salicylic acid (SA)-related pathways. Real-time quantitative PCR (RT-qPCR) revealed that the expression profiles of DEGs were consistent with the results from RNA sequencing analysis. Eight candidate genes encoding GSH, Cys, Gly, BR, and SA were associated with detoxification of Cd and were selected for further screening. A schematic model to explain the involvement of DEGs and N in the Cd-responsive regulatory network is proposed. This study represents the first comprehensive transcriptome-based characterization of N- and Cd-responsive DEGs in poplar. These results provide fundamental insight into the molecular mechanism of N assistance in Cd detoxification. In addition, the results of this study build a solid foundation for further genetic manipulation of Cd accumulation in plants and for the development of phytoremediation approaches to reclaim Cd-contaminated soils.

To date, several species of Asteraceae have been considered as Cd-accumulators. However, little information on the Cd tolerance and associated mechanisms of Asteraceae species Cosmos bipinnatus, is known. Presently, several physiological indexes and transcriptome profiling under Cd stress were investigated. C. bipinnatus exhibited strong Cd tolerance and recommended as a Cd-accumulator, although the biomasses were reduced by Cd. Meanwhile, Cd stresses reduced Zn and Ca uptake, but increased Fe uptake. Subcellular distribution indicated that the vacuole sequestration in root mainly detoxified Cd under lower Cd stress. Whilst, cell wall binding and vacuole sequestration in root co-detoxified Cd under high Cd exposure. Meanwhile, 66,407 unigenes were assembled and 41,674 (62.75%) unigenes were annotated in at least one database. 2,658 DEGs including 1,292 up-regulated unigenes and 1,366 down-regulated unigenes were identified under 40 μmol/L Cd stress. Among of these DEGs, ZIPs, HMAs, NRAMPs and ABC transporters might participate in Cd uptake, translocation and accumulation. Many DEGs participating in several processes such as cell wall biosynthesis, GSH metabolism, TCA cycle and antioxidant system probably play critical roles in cell wall binding, vacuole sequestration and detoxification. These results provided a novel insight into the physiological and transcriptome response to Cd in C. bipinnatus seedlings.

Late embryogenesis abundant (LEA) proteins have been identified in a wide range of organisms and are believed to play a role in the adaptation of plants to stress conditions. In this study, we performed genome-wide identification of LEA proteins and their coding genes in Moso bamboo (Phyllostachys edulis) of Poaceae. A total of 23 genes encoding LEA proteins (PeLEAs) were found in P. edulis that could be classified to six groups based on Pfam protein family and homologous analysis. Further in silico analyses of the structures, gene amount, and biochemical characteristics were conducted and compared with those of O. sativa (OsLEAs), B. distachyon (BdLEAs), Z. mays (ZmLEAs), S. bicolor (SbLEAs), Arabidopsis, and Populus trichocarpa. The less number of PeLEAs was found. Evolutionary analysis revealed orthologous relationship and colinearity between P. edulis, O. sativa, B. distachyon, Z. mays, and S. bicolor. Analyses of the non-synonymous (Ka) and synonymous (Ks)substitution rates and their ratios indicated that the duplication of PeLEAs may have occurred around 18.8 million years ago (MYA), and divergence time of LEA family among the P. edulis-O. sativa and P. edulis-B. distachyon, P. edulis-S. bicolor, and P. edulis-Z. mays was approximately 30 MYA, 36 MYA, 48 MYA, and 53 MYA, respectively. Almost all PeLEAs contain ABA- and (or) stress-responsive regulatory elements. Further RNA-seq analysis revealed approximately 78% of PeLEAs could be up-regulated by dehydration and cold stresses. The present study makes insights into the LEA family in P. edulis and provides inventory of stress-responsive genes for further functional validation and transgenic research aiming to plant genetic improvement of abiotic stress tolerance.

The red-leaf coloration of Quanhong poplar (QHP) (Populus deltoides), resulting from a bud sport, is a distinctive trait conferring high ornamental value. However, the underlying molecular coloration mechanism of the red-leaf poplar remains unknown. In this study, tissue buds and leaves from mutant QHP(red)and its wild-type progenitor L2025 (green) were used to study the coloration mechanism by high-throughput RNA sequencing and comparative analysis of the transcriptomes. A total of 12,000 differentially expressed genes (DEGs) were obtained. Functional enrichment using Gene Ontology (GO) and, Genes and Genomes (KEGG) annotations showed that 4951 bud DEGs and 1927 leaf DEGs participate in many important biological and metabolic pathways, including anthocyanin biosynthesis. Importantly, some structural genes that contribute to photosynthesis were down-regulated, and some candidate genes involved in the biosynthesis of abscisic acid (ABA), ethylene and anthocyanin were up-regulated in the QHP mutant. The DEGs identified provided insight into the novel traits of the mutant. The unigene dataset that was used to discover candidate genes provides a comprehensive resource for molecular research in red-leaf poplar and may provide insight into coloration of other woody plants.

An unusually severe snow disaster in southern China in 2008 exposed variation among different species of bamboo: some species were highly tolerant to low-temperature damage, but some suffered extensive damage or death. Therefore, this study was conducted to determine the effects of cold stress on endogenous hormones and the expression of homologs of CBF 1 in four bamboo species differing in their tolerance to cold. All four bamboo species were subjected to cold stress with a temperature gradient (10, 5, 0, −5, and −10°C), and each low temperature treatment was maintained for 48 h. Results showed that ABA, GA1, and GA4 were significantly affected by cold stress: ABA increased with cold stress in all species, while GA1 and GA4 reduced with cold stress. ABA levels and the ratio of ABA/(GA1 + GA4) in leaves of Neosinocalamus affinis and Bambusa rigida were both higher than those of hybrid bamboo (Bambusa pervariabilis × Dendrocalamopsis grandis) and Dendrocalamus latiflorus for all treatments, while GA1 and GA4 were conversely lower as compared to the hybrid variety and D. latiflorus. Moreover, CBF 1 homolog was up-regulated during cold stress, with higher expression levels in the leaves of cold-tolerant species than cold-sensitive ones. Results revealed that high levels of ABA and CBF 1 , as well as the ABA/GAs balance, are important in increased plant resistance to cold stress.

Despite numerous reports implicating nitric oxide (NO) in the environmental-stress responses of plants, the specific metabolic and ionic mechanisms of NO-mediated adaptation to metal stress remain unclear. Here, the impacts of copper (Cu) and NO donor (SNP, 50 μM) alone or in combination on the well-known medicinal plant Catharanthus roseus L. were investigated. Our results showed that Cu markedly increased Cu 2+ accumulation, decreased NO production, and disrupted mineral equilibrium and proton pumps, thereby stimulating a burst of ROS; in addition, SNP ameliorates the negative toxicity of Cu, and cPTIO reverses this action. Furthermore, the accumulations of ROS and NO resulted in reciprocal changes. Interestingly, nearly all of the investigated amino acids and the total phenolic content in the roots were promoted by the SNP treatment but were depleted by the Cu + SNP treatment, which is consistent with the self-evident increases in phenylalanine ammonia-lyase activity and total soluble phenol content induced by SNP. Unexpectedly, leaf vincristine and vinblastine as well as the total alkaloid content (ca. 1.5-fold) were decreased by Cu but markedly increased by SNP (+38% and +49% of the control levels). This study provides the first evidence of the beneficial behavior of NO, rather than other compounds, in depleting Cu toxicity by regulating mineral absorption, reestablishing ATPase activities, and stimulating secondary metabolites.

The proteins containing the TIFY domain belong to a plant-specific family of putative transcription factors and could be divided into four subfamilies: ZML, TIFY, PPD and JAZ. They not only function as key regulators of jasmonate hormonal response, but are also involved in responding to abiotic stress. In this study, we identified 24 TIFY genes (PeTIFYs) in Moso bamboo (Phyllostachys edulis) of Poaceae by analyzing the whole genome sequence. OnePeTIFYbelongs to TIFY subfamily, 18 and five belong to JAZ and ZML subfamilies, respectively. Two equivocal gene models were re-predicted and a putative retrotransposition event was found in a ZML protein. The distribution and conservation of domain or motif, and gene structure were also analyzed. Phylogenetic analysis with TIFY proteins ofArabidopsisandOryza sativaindicated that JAZ subfamily could be further divided to four groups. Evolutionary analysis revealed intragenomic duplication and orthologous relationship betweenP. edulis,O. sativa, andB. distachyon. Calculation of the non-synonymous (Ka) and synonymous (Ks) substitution rates and their ratios indicated that the duplication ofPeTIFYmay have occurred around 16.7 million years ago (MYA), the divergence time of TIFY family among theP. edulis-O. sativa,P. edulis-B. distachyon,andO. sativa-B. distachyonwas approximately 39 MYA, 39 MYA, and 45 MYA, respectively. They appear to have undergone extensive purifying selection during evolution. Transcriptome sequencing revealed that more than 50% ofPeTIFYgenes could be up-regulated by cold and dehydration stresses, and somePeTIFYsalso share homology to know TIFYs involved in abiotic stress tolerance. Our results made insights into TIFY family of Moso bamboo, an economically important non-timber forest resource, and provided candidates for further identification of genes involved in regulating responses to abiotic stress.