Cloning and Preliminary Functional Analysis of PeUGE Gene from Moso Bamboo (Phyllostachys edulis)

Identification and Expression Analyses of Invertase Genes in Moso Bamboo Reveal Their Potential Drought Stress Functions

Invertases (INVs) can irreversibly hydrolyze sucrose into fructose and glucose, which play principal roles in carbon metabolism and responses to various stresses in plants. However, little is known about the INV family in bamboos, especially their potential function in drought stress. In this study, 29 PeINVs were identified in moso bamboo (Phyllostachys edulis). They were clustered into alkaline/neutral invertase (NINV) and acid invertase (AINV) groups based on the gene structures, conserved motifs, and phylogenetic analysis results. The collinearity analysis showed nine segmental duplication pairs within PeINVs, and 25 pairs were detected between PeINVs and OsINVs. PeINVs may have undergone strong purification selection during evolution, and a variety of stress and phytohormone-related regulatory elements were found in the promoters of PeINVs. The tissue-specific expression analysis showed that PeINVs were differentially expressed in various moso bamboo tissues, which suggested that they showed functional diversity. Both the RNA-seq and quantitative real-time PCR results indicated that four PeINVs were significantly upregulated under drought stress. Co-expression network and Pearson’s correlation coefficient analyses showed that these PeINVs co-expressed positively with sugar and water transport genes (SWTGs), and the changes were consistent with sugar content. Overall, we speculate that the identified PeINVs are spatiotemporally expressed, which enables them to participate in moso bamboo growth and development. Furthermore, PeINVs, together with SWTGs, also seem to play vital roles in the response to drought stress. These results provide a comprehensive information resource for PeINVs, which will facilitate further study of the molecular mechanism underlying PeINVs involvement in the response to drought stress in moso bamboo.

A bamboo leaf-specific aquaporin gene PePIP2;7 is involved in abiotic stress response

PePIP2;7, a leaf-specific aquaporin gene in bamboo, is upregulated under abiotic stresses. Overexpressing PePIP2;7 confers abiotic stresses tolerance in transgenic Arabidopsis plant and yeast. Aquaporins (AQPs) participate in the regulation of water balance in plants. However, the function of AQPs in bamboo remains unclear. Here, PePIP2;7 was identified as a leaf-specific aquaporin gene in moso bamboo based on the expression analysis of transcriptome data and PCR. In situ hybridization further indicated that PePIP2;7 was mainly expressed in mesophyll cells of mature leaves, while in immature leaves it was dominant in blade edge cells followed by mesophyll cells. Interestingly, PePIP2;7 was strongly expressed in the mesophyll cells near bulliform cells of immature leaves, suggesting that PePIP2;7 might function in water transport and contribute to leaf unfolding. The transient expression assay showed that PePIP2;7 was a plasma membrane intrinsic protein. Furthermore, PePIP2;7 was upregulated under abiotic stresses such as high light, drought, and NaCl. Compared with Col-0, transgenic Arabidopsis plants overexpressing PePIP2;7 had better seed germination rate, longer taproot length, higher SOD activity, and lower MDA content under abiotic stresses. Besides, yeasts expressing PePIP2;7 also had higher tolerance to stress compared to the control. Taken together, our results show that PePIP2;7 is leaf-specific and involved in stress response, which provides new insights into aquaporin function in bamboo.

Biosynthesis and Transport of Nucleotide Sugars for Plant Hemicellulose

Hemicellulose is entangled with cellulose through hydrogen bonds and meanwhile acts as a bridge for the deposition of lignin monomer in the secondary wall. Therefore, hemicellulose plays a vital role in the utilization of cell wall biomass. Many advances in hemicellulose research have recently been made, and a large number of genes and their functions have been identified and verified. However, due to the diversity and complexity of hemicellulose, the biosynthesis and regulatory mechanisms are yet unknown. In this review, we summarized the types of plant hemicellulose, hemicellulose-specific nucleotide sugar substrates, key transporters, and biosynthesis pathways. This review will contribute to a better understanding of substrate-level regulation of hemicellulose synthesis.

Engineering Drought Resistance in Forest Trees

Climatic stresses limit plant growth and productivity. In the past decade, tree improvement programs were mainly focused on yield but it is obvious that enhanced stress resistance is also required. In this review we highlight important drought avoidance and tolerance mechanisms in forest trees. Genomes of economically important trees species with divergent resistance mechanisms can now be exploited to uncover the mechanistic basis of long-term drought adaptation at the whole plant level. Molecular tree physiology indicates that osmotic adjustment, antioxidative defense and increased water use efficiency are important targets for enhanced drought tolerance at the cellular and tissue level. Recent biotechnological approaches focused on overexpression of genes involved in stress sensing and signaling, such as the abscisic acid core pathway, and down-stream transcription factors. By this strategy, a suite of defense systems was recruited, generally enhancing drought and salt stress tolerance under laboratory conditions. However, field studies are still scarce. Under field conditions trees are exposed to combinations of stresses that vary in duration and magnitude. Variable stresses may overrule the positive effect achieved by engineering an individual defense pathway. To assess the usability of distinct modifications, large-scale experimental field studies in different environments are necessary. To optimize the balance between growth and defense, the use of stress-inducible promoters may be useful. Future improvement programs for drought resistance will benefit from a better understanding of the intricate networks that ameliorate molecular and ecological traits of forest trees.

Engineering Drought Resistance in Forest Trees

Climatic stresses limit plant growth and productivity. In the past decade, tree improvement programs were mainly focused on yield but it is obvious that enhanced stress resistance is also required. In this review we highlight important drought avoidance and tolerance mechanisms in forest trees. Genomes of economically important trees species with divergent resistance mechanisms can now be exploited to uncover the mechanistic basis of long-term drought adaptation at the whole plant level. Molecular tree physiology indicates that osmotic adjustment, antioxidative defense and increased water use efficiency are important targets for enhanced drought tolerance at the cellular and tissue level. Recent biotechnological approaches focused on overexpression of genes involved in stress sensing and signaling, such as the abscisic acid core pathway, and down-stream transcription factors. By this strategy, a suite of defense systems was recruited, generally enhancing drought and salt stress tolerance under laboratory conditions. However, field studies are still scarce. Under field conditions trees are exposed to combinations of stresses that vary in duration and magnitude. Variable stresses may overrule the positive effect achieved by engineering an individual defense pathway. To assess the usability of distinct modifications, large-scale experimental field studies in different environments are necessary. To optimize the balance between growth and defense, the use of stress-inducible promoters may be useful. Future improvement programs for drought resistance will benefit from a better understanding of the intricate networks that ameliorate molecular and ecological traits of forest trees.

Antifatigue Effect of Luteolin-6-C-Neohesperidoside on Oxidative Stress Injury Induced by Forced Swimming of Rats through Modulation of Nrf2/ARE Signaling Pathways

Luteolin-6-C-neohesperidoside (LN) is a flavonoid isolated from moso bamboo leaf. This study was performed to evaluate the antifatigue effect of LN on a rat model undergoing the weight-loaded forced swimming test (FST). Briefly, male Sprague-Dawley rats (20-22 weeks old) were forced to undertake exhaustive swimming every other day for 3 weeks. Each swimming session was followed by the administration of distilled water, LN (25-75 mg/kg), or ascorbic acid (100 mg/kg) 1 h later. Oral administration of LN significantly improved exercise endurance; normalized alterations in energy metabolic markers; and decreased serum lactic acid, lactate dehydrogenase, and blood urea nitrogen levels of rats that underwent FST. Moreover, LN enhanced the activities of antioxidant enzymes and antioxidant capacity, as measured by enzyme activity assays, RT-PCR, and Western blotting, as well as decreasing the levels of proinflammatory cytokines such as tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 and increasing the level of anti-inflammatory (IL-10) in the liver and skeletal muscle. These results suggested that LN reduces both physical and mental effects of chronic fatigue, probably by attenuating oxidative stress injury and inflammatory responses in the liver and skeletal muscle. This study thus supports the use of LN in functional foods for antifatigue and antioxidant effects.

The bamboo aquaporin gene PeTIP4;1-1 confers drought and salinity tolerance in transgenic Arabidopsis

PeTIP4;1-1, an aquaporin gene involved in bamboo shoot growth, is regulated by abiotic stresses. Overexpression of PeTIP4;1-1 confers drought and salinity tolerance in transgenic Arabidopsis. Aquaporins play a central role in numerous physiological processes throughout plant growth and development. PeTIP4;1-1, an aquaporin gene isolated from moso bamboo (Phyllostachys edulis), comprises an open reading frame (ORF) of 756 bp encoding a peptide of 251 amino acids. The genomic sequence corresponding to the ORF of PeTIP4;1-1 was 1777 bp and contained three exons separated by two introns. PeTIP4;1-1 was constitutively expressed at the highest level in culms, and the expression level was elevated with increasing height of the bamboo shoot. PeTIP4;1-1 was significantly up-regulated in response to drought and salinity stresses in bamboo roots and leaves. To investigate the role of PeTIP4;1-1 in response to drought and salinity stresses, transgenic Arabidopsis plants overexpressing PeTIP4;1-1 under the control of CaMV 35S promoter were generated and subjected to morphological and physiological assays. Compared with Col-0, the transgenic plants showed enhanced tolerance to drought and salinity stresses and produced longer taproots, which had more green leaves, higher F _v/F _m and NPQ values, higher activities of SOD, POD and CAT, lower MDA concentration and higher water content. Transcript levels of three stress-related genes (AtP5CS, AtNHX1 and AtLEA) were enhanced. These results indicated that PeTIP4;1-1 might play an important function in response to drought and salinity stresses, and is a candidate gene for breeding of stress tolerance in other crops through genetic engineering.