Cucumber Phospholipase D alpha gene overexpression in tobacco enhanced drought stress tolerance by regulating stomatal closure and lipid peroxidation

Genome-wide identification of the Phospholipase D (PLD) gene family in Chinese white pear (Pyrus bretschneideri) and the role of PbrPLD2 in drought resistance

The Chinese white pear (Pyrus bretschneideri), a vital fruit crop, is highly susceptible to abiotic stresses, especially drought, which poses a major threat to its growth and productivity. Phospholipase D (PLD) genes are pivotal in orchestrating plant responses to abiotic stresses, acting as key regulators in stress adaptation mechanisms. This study systematically identified and functionally characterized the entire PLD gene family in P. bretschneideri through a comprehensive genome-wide analysis. A total of 20 PbrPLD genes were identified, and they were categorized into five subfamilies based on phylogenetic analysis. chromosome localization, gene structure, and conserved motif analyses revealed that these genes have diverse evolutionary histories. Cis-acting element analysis and expression profiling under drought stress indicated that several PbrPLD genes, particularly PbrPLD2, are strongly induced by drought. Overexpression of PbrPLD2 in both Arabidopsis thaliana and pear demonstrated enhanced drought tolerance through improved stomatal closure and increased expression of drought-responsive genes. These findings highlight the critical role of PbrPLD2 in drought resistance and provide a theoretical and experimental foundation for molecular breeding in pear and other fruit crops.

H2S is involved in drought-mediated stomatal closure through PLDα1 in Arabidopsis

MAIN CONCLUSION

PLDα1 promoted H2S production by positively regulating the expression of LCD. Stomatal closure promoted by PLDα1 required the accumulation of H2S under drought stress. Phospholipase Dα1 (PLDα1) acting as one of the signal enzymes can respond to drought stress. It is well known that hydrogen sulfide (H2S) plays an important role in plant responding to biotic or abiotic stress. In this study, the functions and relationship between PLDα1 and H2S in drought stress resistance in Arabidopsis were explored. Our results indicated that drought stress promotes PLDα1 and H2S production by inducing the expression of PLDα1 and LCD genes. PLDα1 and LCD enhanced plant tolerance to drought by regulating membrane lipid peroxidation, proline accumulation, H2O2 content and stomatal closure. Under drought stress, the H2O2 content of PLDα1-deficient mutant (pldα1), L-cysteine desulfhydrase (LCD)-deficient mutant (lcd) was higher than that of ecotype (WT), the stomatal aperture of pldα1 and lcd was larger than that of WT. The transcriptional and translational levels of LCD were lower in pldα1 than that in WT. Exogenous application of the H2S donor NaHS or GYY reduced the stomatal aperture of WT, pldα1, PLDα1-CO, and PLDα1-OE lines, while exogenous application of the H2S scavenger hypotaurine (HT) increased the stomatal aperture. qRT-PCR analysis of stomatal movement-related genes showed that the expression of CAX1, ABCG5, SCAB1, and SLAC1 genes in pldα1 and lcd were down-regulated, while ACA1 and OST1 gene expression was significantly up-regulated. Thus, PLDα1 and LCD are required for stomatal closure to improve drought stress tolerance.

Pivotal role of heterotrimeric G protein in the crosstalk between sugar signaling and abiotic stress response in plants

Heterotrimeric G-proteins are key modulators of multiple signaling and developmental pathways in plants, in which they act as molecular switches to engage in transmitting various stimuli signals from outside into the cells. Substantial studies have identified G proteins as essential components of the organismal response to abiotic stress, leading to adaptation and survival in plants. Meanwhile, sugars are also well acknowledged key players in stress perception, signaling, and gene expression regulation. Connections between the two significant signaling pathways in stress response are of interest to a general audience in plant biology. In this article, advances unraveling a pivotal role of G proteins in the process of sugar signals outside the cells being translated into the operation of autophagy in cells during stress are reviewed. In addition, we have presented recent findings on G proteins regulating the response to drought, salt, alkali, cold, heat and other abiotic stresses. Perspectives on G-protein research are also provided in the end. Since G protein signaling regulates many agronomic traits, elucidation of detailed mechanism of the related pathways would provide useful insights for the breeding of abiotic stress resistant and high-yield crops.

Effect of Arbuscular Mycorrhizal Fungi and Rock Phosphate on Growth, Physiology, and Biochemistry of Carob under Water Stress and after Rehydration in Vermicompost-Amended Soil

In the Mediterranean region, reforestation programs record failures following successive drought periods. The use of different plant-growth-promoting amendments and the understanding of drought-induced physiological and biochemical responses of carob will contribute to the reforestation program's success. In this study, the effects of arbuscular-mycorrhizal-fungi (AMF), vermicompost (VC), and rock phosphate (RP) on carob seedlings under drought stress (DS) and recovery (REC) conditions were evaluated. A greenhouse experiment was conducted with carob seedlings grown in the presence of AMF, VC, and RP, applied alone or in combination under well-watered (WW), DS (by stopping irrigation for 12 days), and recovery (REC) conditions. The obtained results indicated that the triple combination (AMF + VC + RP) presented the highest improvement in water potential, photosynthetic pigment content, stomatal conductance, and chlorophyll fluorescence compared to the controls under DS and after REC. In addition, this combination resulted in improved tolerance of carob seedlings to DS and a high potential for rapid recovery after rehydration due to a high accumulation of sugars, proteins, and antioxidant enzymes. In summary, the results underline the importance of inoculating carob with AMF in combination with (in)-organic amendments in improving its tolerance to DS and its recovery performances.

Effects of the synergistic treatments of arbuscular mycorrhizal fungi and trehalose on adaptability to salt stress in tomato seedlings

Arbuscular mycorrhizal fungi (AMF) could establish symbiosis with plant roots, which enhances plant resistance to various stresses, including drought stress and salt stress. Besides AMF, chemical stimulants such as trehalose (Tre) can also play an important role in helping plants alleviate damage of adversity. However, the mechanism of the effect of AMF combined with chemicals on plant stress resistance is unclear. The objective of this study was to explore the synergistic effects of Claroideoglomus etunicatum AMF and exogenous Tre on the antioxidant system, osmoregulation, and resistance-protective substance in plants in response to salt stress. Tomato seedlings were inoculated with Claroideoglomus etunicatum and combined with exogenous Tre in a greenhouse aseptic soil cultivation experiment. We measured the arbuscular mycorrhizal symbiont development, organic matter content, and antioxidant enzyme activity in tomato seedlings. Both AMF and Tre improved the synthesis of chlorophyll content in tomato seedlings; regulated the osmotic substance including soluble sugars, soluble protein, and proline of plants; and increased the activity of superoxide dismutase, peroxidase, and catalase. The combination of AMF and Tre also reduced the accumulation of malondialdehyde and alleviated the damage of harmful substances to plant cells in tomato seedlings. We studied the effects of AMF combined with extraneous Tre on salt tolerance in tomato seedlings, and the results showed that the synergistic treatment of AMF and Tre was more efficient than the effects of AMF inoculation or Tre spraying separately by regulating host substance synthesis, osmosis, and antioxidant enzymes. Our results indicated that the synergistic effects of AMF and Tre increased the plant adaptability against salt damage by enhancing cell osmotic protection and cell antioxidant capacity.

IMPORTANCE

AMF improve the plant adaptability to salt resistance by increasing mineral absorption and reducing the damage of saline soil. Trehalose plays an important role in plant response to salt damage by regulating osmotic pressure. Together, the use of AMF and trehalose in tomato seedlings proved efficient in regulating host substance synthesis, osmosis, and antioxidant enzymes. These synergistic effects significantly improved seedling adaptability to salt stress by enhancing cell osmotic protection and cell antioxidant capacity, ultimately reducing losses to crops grown on land where salinization has occurred.

Phenotyping and metabolome analysis reveal the role of AdoMetDC and Di19 genes in determining acquired tolerance to drought in rice

Water-saving attempts for rice cultivation often reduce yields. Maintaining productivity under drought is possible when rice genotypes are bred with improved metabolism and spikelet fertility. Although attempts have been made to introgress water mining and water use efficiency traits, combining acquired tolerance traits (ATTs), that is, specific traits induced or upregulated to better tolerate severe stress, appears equally important. In our study, we screened 90 rice germplasm accessions that represented the molecular and phenotypic variations of 851 lines of the 3 K rice panel. Utilising phenomics, we identified markers linked to ATTs through association analysis of over 0.2 million SNPs derived from whole-genome sequences. Propensity to respond to 'induction' stress varied significantly among genotypes, reflecting differences in cellular protection against oxidative stress. Among the ATTs, the hydroxyl radical and proline contents exhibited the highest variability. Furthermore, these significant variations in ATTs were strongly correlated with spikelet fertility. The 43 significant markers associated with ATTs were further validated using a different subset of contrasting genotypes. Gene expression studies and metabolomic profiling of two well-known contrasting genotypes, APO (tolerant) and IR64 (sensitive), identified two ATT genes: AdoMetDC and Di19. Our study highlights the relevance of polyamine biosynthesis in modulating ATTs in rice. Genotypes with superior ATTs and the associated markers can be effectively employed in breeding rice varieties with sustained spikelet fertility and grain yield under drought.

Proline metabolism as a mechanism for the energy dissipation in VaP5CSF129A transgenic tobacco plants under water deficit

In plants, proline accumulation in cells is a common response to alleviate the stress caused by water deficits. It has been shown that foliar proline spraying, as well as its overaccumulation in transgenic plants can increase drought tolerance, as proline metabolism plays important roles in cell redox balance and on energy dissipation pathways. The aim of this work was to evaluate the role of exogenous proline application or its endogenous overproduction as a potential mechanism for energy dissipation. For this, wild-type and VaP5CSF129A transgenic tobacco plants were sprayed with proline (10 mM) and submitted to water deficit. Changes in plant physiology and biochemistry were evaluated. Transcriptional changes in the relative expression of genes involved in proline synthesis and catabolism, NAD (P)-dependent malate dehydrogenase (NAD(P)-MDH), alternative oxidase (AOX), and VaP5CSF129A transgene were measured. Exogenous proline reduced the negative effects of water deficit on photosynthetic activity in both genotypes; with the transgenic plants even less affected. Water deficit caused an increase in the relative expression of proline biosynthesis genes. On the other hand, the expression of catabolism genes decreased, primarily in transgenic plants. Exogenous proline reduced activity of the NADP-MDH enzyme and decreased expression of the AOX and NADP-MDH genes, mainly in transgenic plants under water stress. Finally, our results suggest that proline metabolism could act as a complementary/compensatory mechanism for the energy dissipation pathways in plants under water deficit.

Proteomics approach to investigating osmotic stress effects on pistachio

Osmotic stress can occur due to some stresses such as salinity and drought, threatening plant survival. To investigate the mechanism governing the pistachio response to this stress, the biochemical alterations and protein profile of PEG-treated plants was monitored. Also, we selected two differentially abundant proteins to validate via Real-Time PCR. Biochemical results displayed that in treated plants, proline and phenolic content was elevated, photosynthetic pigments except carotenoid decreased and MDA concentration were not altered. Our findings identified a number of proteins using 2DE-MS, involved in mitigating osmotic stress in pistachio. A total of 180 protein spots were identified, of which 25 spots were altered in response to osmotic stress. Four spots that had photosynthetic activities were down-regulated, and the remaining spots were up-regulated. The biological functional analysis of protein spots exhibited that most of them are associated with the photosynthesis and metabolism (36%) followed by stress response (24%). Results of Real-Time PCR indicated that two of the representative genes illustrated a positive correlation among transcript level and protein expression and had a similar trend in regulation of gene and protein. Osmotic stress set changes in the proteins associated with photosynthesis and stress tolerance, proteins associated with the cell wall, changes in the expression of proteins involved in DNA and RNA processing occur. Findings of this research will introduce possible proteins and pathways that contribute to osmotic stress and can be considered for improving osmotic tolerance in pistachio.

PIN1 regulates epidermal cells development under drought and salt stress using single-cell analysis

Over the course of evolution, plants have developed plasticity to acclimate to environmental stresses such as drought and salt stress. These plant adaptation measures involve the activation of cascades of molecular networks involved in stress perception, signal transduction and the expression of stress related genes. Here, we investigated the role of the plasma membrane-localized transporter of auxin PINFORMED1 (PIN1) in the regulation of pavement cells (PCs) and guard cells (GCs) development under drought and salt stress conditions. The results showed that drought and salt stress treatment affected the development of PCs and GCs. Further analysis identified the different regulation mechanisms of PIN1 in regulating the developmental patterns of PCs and GCs under drought and salt stress conditions. Drought and salt stress also regulated the expression dynamics of PIN1 in pif1/3/4/5 quadruple mutants. Collectively, we revealed that PIN1 plays a crucial role in regulating plant epidermal cells development under drought and salt stress conditions, thus contributing to developmental rebustness and plasticity.

Interactions between hydrogen sulphide and rhizobia modulate the physiological and metabolism process during water deficiency-induced oxidative defense in soybean

Hydrogen sulphide (H₂ S), a new gas signal molecule, participates in the regulation of various abiotic stresses in plants. However, how the tandem working of H₂ S and rhizobia affects the adaptation of soybean to water deficiency is still unclear. In this study, we investigated the adaptation mechanism of H₂ S and rhizobia in soybean to water deficiency. Our results revealed that H₂ S and rhizobia jointly enhanced the leaf chlorophyll content and relative water content in plants, and caused an increase in the biomass of soybean seedlings under water deficiency. Besides, in the absence of water, H₂ S enhanced the biomass by affecting the number of nodules and nitrogenase activity during vegetative growth. The expression of nodulation marker genes including early nodulin 40 (GmENOD40), ERF required for nodulation (GmERN) and nodulation inception genes (GmNIN1a, GmNIN2a and GmNIN2b) were upregulated by H₂ S and rhizobia in the nodules. Moreover, the combined effect of H₂ S and rhizobia was proved to affect the enzyme activities and gene expression level of antioxidants, as well as osmotic protective substance content and related gene expression levels under water deficiency in soybean seedlings. In addition, the metabolomic results suggested that the combined effect of H₂ S and rhizobia remarkably promoted the contents of lipids and lipid-like molecules. Our results indicated that H₂ S and rhizobia synergistically reduced the oxidative damage caused by water deficiency through increasing the accumulation of metabolites and strengthening the plant antioxidant capacity.

Characterization and Expression of Phospholipase D Putatively Involved in Colletotrichummusae Disease Development of Postharvest Banana Fruit

Phospholipase D (PLD) in plants plays an important role in growth, development, and stress response. The effect of hexanal on PLD in banana fruit responding to Colletotrichum musae infection remains poorly understood. In this study, four putative PLD genes, named as MaPLD1, MaPLD2, MaPLD3, and MaPLD4 were identified from banana fruit. The four MaPLDs can be classified into three of the seven known PLD families according to sequence characterization. Their deduced amino acid sequences displayed homology of PLDs from other plant species. Furthermore, the specific expression analysis of PLD genes in banana fruit in response to infection in C. musae was studied and the response relationship between PLD family members and banana fruit under anthracnose stress was clarified. Changes in both the activity of PLD and PLC, and the connection between hexanal and phospholipases in the banana fruit C. musae infection were compared. The results showed that the incidence of disease in banana inoculated with C. musae was dramatically increased after 6 days of storage, the activation of PLD and PLC in infected anthracnose fruit before disease development, and that this activation was inhibited by hexanal treatment, which suggested that both enzymes play a protective role in banana fruit to cope with C. musae infection and the participation of hexanal in their regulation. Of the four MaPLD genes, the anthracnose had a stronger effect on MaPLD1 and MaPLD4. These data demonstrated that hexanal treatment could enhance fruit disease resistance to C. musae, and that PLD could take part in the disease defensive system of harvested banana fruit to C. musae by modulating the metabolism of cell membrane lipids, and thus suppress disease development in C. musae -inoculated banana during storage.

Phosphatidylinositol 3-phosphate regulates SCAB1-mediated F-actin reorganization during stomatal closure in Arabidopsis

Stomatal movement is critical for plant responses to environmental changes and is regulated by the important signaling molecule phosphatidylinositol 3-phosphate (PI3P). However, the molecular mechanism underlying this process is not well understood. In this study, we show that PI3P binds to stomatal closure-related actin-binding protein1 (SCAB1), a plant-specific F-actin-binding and -bundling protein, and inhibits the oligomerization of SCAB1 to regulate its activity on F-actin in guard cells during stomatal closure in Arabidopsis thaliana. SCAB1 binds specifically to PI3P, but not to other phosphoinositides. Treatment with wortmannin, an inhibitor of phosphoinositide kinase that generates PI3P, leads to an increase of the intermolecular interaction and oligomerization of SCAB1, stabilization of F-actin, and retardation of F-actin reorganization during abscisic acid (ABA)-induced stomatal closure. When the binding activity of SCAB1 to PI3P is abolished, the mutated proteins do not rescue the stability and realignment of F-actin regulated by SCAB1 and the stomatal closure in the scab1 mutant. The expression of PI3P biosynthesis genes is consistently induced when the plants are exposed to drought and ABA treatments. Furthermore, the binding of PI3P to SCAB1 is also required for vacuolar remodeling during stomatal closure. Our results illustrate a PI3P-regulated pathway during ABA-induced stomatal closure, which involves the mediation of SCAB1 activity in F-actin reorganization.

Long-distance control of pumpkin rootstock over cucumber scion under drought stress as revealed by transcriptome sequencing and mobile mRNAs identifications

Grafting with pumpkin rootstock is commonly used not only to improve the quality of cucumber fruits but also to confer biotic or abiotic stress tolerance. However, the molecular mechanism of grafted cucumbers to drought stress and the possible roles of mobile mRNAs to improve stress tolerance have remained obscure. Hence, we conducted transcriptome sequencing and combined it with morpho-physiological experiments to compare the response of homografts (cucumber as scion and rootstock) (C) and heterografts (cucumber as scion and pumpkin as rootstock) (P) to drought stress. After applying drought stress, homografts and heterografts expressed 2960 and 3088 genes in response to drought stress, respectively. The identified DEGs in heterografts under drought stress were categorized into different stress-responsive groups, such as carbohydrate metabolism (involved in osmotic adjustment by sugar accumulation), lipid and cell wall metabolism (involved in cell membrane integrity by a reduction in lipid peroxidation), redox homeostasis (increased antioxidant enzymes activities), phytohormone (increased ABA content), protein kinases and transcription factors (TFs) using MapMan software. Earlier and greater H2O2 accumulation in xylem below the graft union was accompanied by leaf ABA accumulation in heterografts in response to drought stress. Greater leaf ABA helped heterografted cucumbers to sense and respond to drought stress earlier than homografts. The timely response of heterografts to drought stress led to maintain higher water content in the leaves even in the late stage of drought stress. The identified mobile mRNAs (mb-mRNAs) in heterografts were mostly related to photosynthesis which would be the possible reason for improved chlorophyll content and maximum photochemical efficiency of PSII (Fv/Fm). The existence of some stress-responsive pumpkin (rootstock) mRNAs in cucumber (scion), such as heat shock protein (HSP70, a well-known stress-responsive gene), led to the higher proline accumulation than homografts. The expression of the mobile and immobile stress-responsive mRNAs and timely response of heterografts to drought stress could improve drought tolerance in pumpkin-rooted plants.

The mechanisms of silicon on maintaining water balance under water deficit stress

Water deficit stress severely threatens crop yield and numerous reports have shown silicon could enhance plants resistance to water deficit. One of the most important mechanisms is that silicon maintains the water balance. In this review, we summarized advanced research to elucidate the effect of silicon on plant water transport processes, including leaf water loss, vessel water transport, and root water uptake. In leaves, the deposition of silica phytolith on cuticle and stomata decreases transpirational water loss under water deficit stress. However, accumulating evidence suggest that silicon maintaining leaf water content is not through reducing water loss, but through osmotic adjustments, enhancing water transport and uptake. Enhancement of stem water transport efficiency by silicon is due to silica phytolith depositing in the cell wall of vessel tubes and pits, which support it avoiding to collapse and embolism, respectively. The improvement of root water uptake capacity by silicon acts as a key role in maintaining water balance. The underlying mechanisms include (i) enlargement of the root water uptake area, (ii) improvement of the water driving force, (iii) the prevention of water loss from root to soil, and (iv) the up-regulation of aquaporin activity. This review provides three simple models to understand the mechanism of silicon on water balance and highlights the future research area.

Plant phospholipase D: novel structure, regulatory mechanism, and multifaceted functions with biotechnological application

Phospholipases D (PLDs) are important membrane lipid-modifying enzymes in eukaryotes. Phosphatidic acid, the product of PLD activity, is a vital signaling molecule. PLD-mediated lipid signaling has been the subject of extensive research leading to discovery of its crystal structure. PLDs are involved in the pathophysiology of several human diseases, therefore, viewed as promising targets for drug design. The availability of a eukaryotic PLD crystal structure will encourage PLD targeted drug designing. PLDs have been implicated in plants response to biotic and abiotic stresses. However, the molecular mechanism of response is not clear. Recently, several novel findings have shown that PLD mediated modulation of structural and developmental processes, such as: stomata movement, root growth and microtubule organization are crucial for plants adaptation to environmental stresses. Involvement of PLDs in regulating membrane remodeling, auxin mediated alteration of root system architecture and nutrient uptake to combat nitrogen and phosphorus deficiencies and magnesium toxicity is established. PLDs via vesicle trafficking modulate cytoskeleton and exocytosis to regulate self-incompatibility (SI) signaling in flowering plants, thereby contributes to plants hybrid vigor and diversity. In addition, the important role of PLDs has been recognized in biotechnologically important functions, including oil/TAG synthesis and maintenance of seed quality. In this review, we describe the crystal structure of a plant PLD and discuss the molecular mechanism of catalysis and activity regulation. Further, the role of PLDs in regulating plant development under biotic and abiotic stresses, nitrogen and phosphorus deficiency, magnesium ion toxicity, SI signaling and pollen tube growth and in important biotechnological applications has been discussed.

Heterotrimeric G protein signalling in plant biotic and abiotic stress response

Heterotrimeric G proteins act as molecular switches to participate in transmitting various stimuli signals from outside of cells. G proteins have three subunits, Gα, Gβ and Gγ, which function mutually to modulate many biological processes in plants, including plant growth and development, as well as biotic and abiotic stress responses. In plants, the number of Gγ subunits is larger than that of the α and β subunits. Based on recent breakthroughs in studies of plant G protein signal perception, transduction and downstream effectors, this review summarizes and analyses the connections between different subunits and the interactions of G proteins with other signalling pathways, especially in plant biotic and abiotic stress responses. Based on current progress and unresolved questions in the field, we also suggest future research directions on G proteins in plants.

Osmotic stress-triggered stomatal closure requires Phospholipase Dδ and hydrogen sulfide in Arabidopsis thaliana

Osmotic stress is one of the main stresses seriously affects the growth and development of plants. Hydrogen sulfide (H₂S) emerges as the third gaseous signal molecule to involve in the complex network of signaling events. Phospholipase Dδ (PLDδ), as signal enzyme, responds to many biotic or abiotic stress responses. In this study, the functions and the relationship of PLDδ and H₂S in stomatal closure induced by osmotic stress were explored. Using the seedlings of ecotype (WT), PLDδ deficient mutant (pldδ), L-cysteine desulfhydrase (LCD) deficient mutant (lcd) and pldδlcd double mutant as materials, the Real-time quantitative PCR (RT-qPCR) and the stomatal aperture were analyzed. Osmotic stress induced the expressions of PLDδ and LCD. The H₂S content and the activities of PLD and LCD ascended in WT under osmotic stress. The phenotypes of pldδ, lcd and pldδlcd were more sensitive to osmotic stress than WT. Compared with pldδ, the stomatal of lcd showed lower sensitivity to osmotic stress, and the stomatal aperture of pldδlcd was similar to that of lcd. Simultaneous application of PA and NaHS resulted in tighter closure of stomatal than application of either PA or NaHS alone. These results suggested that osmotic stress-triggered stomatal closure requires PLDδ and H₂S in A. thaliana. LCD acted downstream of PLDδ to regulate the stomatal closure induced by osmotic stress.

Photochemistry and proteomics of ginger (Zingiber officinale Roscoe) under drought and shading

Drought has become an increasingly serious ecological problem that limits crop production. However, little is known about the response of ginger (Zingiber officinale Roscoe) to drought and shading, especially with respect to photosynthetic electron transport. Here, differential proteomics was used to study the response of ginger to four experimental treatments: control, drought, 50% shading, and the combination of 50% shading and drought. Proteomic analysis suggested that ginger increased cyclic electron flow under drought stress by enhancing the expression of proteins related to photosystem I and cytochrome b6f. Shading significantly increased the expression of proteins related to the light harvesting complex, even under drought stress. In addition, shading increased the expression of proteins related to the oxygen evolution complex, plastocyanin, and ferredoxin-NADP+ reductase (FNR), thereby enhancing the efficiency of photosynthetic electron utilization. The shading and drought combination treatment appeared to enhance ginger's drought tolerance by reducing the expression of FNR and enhancing cyclic electron flow. Photosynthetic and fluorescence parameters showed that drought stress caused non-stomatal limitation of photosynthesis in ginger leaves. Drought stress also significantly reduced the quantum efficiency of photosystem II (Fv/Fm), the non-cyclic electron transfer efficiency of photosystem II (ϕPSII), and photochemical quenching (qP), while simultaneously increasing nonphotochemical quenching (NPQ). The addition of shading improved photosynthetic efficiency under drought. These results provide important baseline information on the photosynthetic mechanisms by which ginger responds to drought and shading. In addition, they provide a theoretical basis for the study of shade cultivation during the arid season.

Genome-Wide Analysis of Phospholipase D Gene Family and Profiling of Phospholipids under Abiotic Stresses in Brassica napus

Oil crop Brassica napus is subjected to environmental stresses such as drought, cold and salt. Phospholipase Ds (PLDs) have vital roles in regulation of plant growth, development and stress tolerance. In this study, 32 BnaPLD genes were identified and classified into six subgroups depending on the conserved protein structures. High similarity in gene and protein structures exists between BnaPLDs and AtPLDs. Gene expression analysis showed that BnaPLDα1s and BnaPLDδs had higher expression than other PLDs. BnaPLDα1 and BnaPLDδ were significantly induced by abiotic stresses including dehydration, NaCl, abscisic acid (ABA) and 4�C. Lipidomic analysis showed that the content of main membrane phospholipids decreased gradually under stresses, except phosphatidylglycerol increased under the treatment of ABA and phosphatidylethanolamine increased under 4�C. Correspondingly, their product of phosphatidic acid increased often with a transient peak at 8 h. The plant height of mutants of PLDα1 was significantly reduced. Agronomic traits such as yield, seed number, silique number and branches were significantly impaired in PLDα1 mutants. These results indicate that there is a large family of PLD genes in B. napus, especially BnaPLDα1s and BnaPLDδs may play important roles in membrane lipids remodeling and maintaining of the growth and stress tolerance of B. napus.