The dehydration- and ABA-inducible germin-like protein CpGLP1 from Craterostigma plantagineum has SOD activity and may contribute to cell wall integrity during desiccation

Genome-wide Characterization of Small Secreted Peptides in Nicotiana tabacum and Functional Assessment of NtLTP25 in Plant Immunity

Small secreted peptides (SSPs), serving as signaling molecules for intercellular communication, play significant regulatory roles in plant growth, development, pathogen immunity, and responses to abiotic stress. Despite several SSPs, such as PIP, PSK, and PSY having been identified to participate in plant immunity, the majority of SSPs remain understudied, necessitating the exploration and identification of SSPs regulating plant immunity from vast genomic resources. Here we systematically characterized 756 putative SSPs across the genome of Nicotiana tabacum. 173 SSPs were further annotated as established SSPs, such as nsLTP, CAPE, and CEP. Furthermore, we detected the expression of 484 putative SSP genes in five tissues, with 83 SSPs displaying tissue-specific expression. Transcriptomic analysis of tobacco roots under plant defense hormones revealed that 46 SSPs exhibited specific responsiveness to salicylic acid (SA), and such response was antagonistically regulated by methyl jasmonate. It's worth noting that among these 46 SSPs, 16 members belong to nsLTP family, and one of them, NtLTP25, was discovered to enhance tobacco's resistance against Phytophthora nicotianae. Overexpression of NtLTP25 in tobacco enhanced the expression of ICS1, subsequently stimulating the biosynthesis of SA and the expression of NPR1 and pathogenesis-related genes. Concurrently, NtLTP25 overexpression activated genes associated with ROS scavenging, consequently mitigating the accumulation of ROS during the subsequent phases of pathogenesis. These discoveries indicate that these 46 SSPs, especially the 16 nsLTPs, might have a vital role in governing plant immunity that relies on SA signaling. This offers a valuable source for pinpointing SSPs involved in regulating plant immunity.

Analysis of Germin-like protein genes family in Vitis vinifera (VvGLPs) using various in silico approaches

Abstract Germin-like proteins (GLPs) play an important role against various stresses. Vitis vinifera L. genome contains 7 GLPs; many of them are functionally unexplored. However, the computational analysis may provide important new insight into their function. Currently, physicochemical properties, subcellular localization, domain architectures, 3D structures, N-glycosylation & phosphorylation sites, and phylogeney of the VvGLPs were investigated using the latest computational tools. Their functions were predicted using the Search tool for the retrieval of interacting genes/proteins (STRING) and Blast2Go servers. Most of the VvGLPs were extracellular (43%) in nature but also showed periplasmic (29%), plasma membrane (14%), and mitochondrial- or chloroplast-specific (14%) expression. The functional analysis predicted unique enzymatic activities for these proteins including terpene synthase, isoprenoid synthase, lipoxygenase, phosphate permease, receptor kinase, and hydrolases generally mediated by Mn+ cation. VvGLPs showed similarity in the overall structure, shape, and position of the cupin domain. Functionally, VvGLPs control and regulate the production of secondary metabolites to cope with various stresses. Phylogenetically VvGLP1, -3, -4, -5, and VvGLP7 showed greater similarity due to duplication while VvGLP2 and VvGLP6 revealed a distant relationship. Promoter analysis revealed the presence of diverse cis-regulatory elements among which CAAT box, MYB, MYC, unnamed-4 were common to all of them. The analysis will help to utilize VvGLPs and their promoters in future food programs by developing resistant cultivars against various biotic (Erysiphe necator and in Powdery Mildew etc.) and abiotic (Salt, drought, heat, dehydration, etc.) stresses.

Establishment of protoplasts transient expression system in Pinellia ternata (Thunb.) Breit

OBJECTIVE

In this study, we established an efficient and rapid transient expression system in the protoplasts of Pinellia ternata (Thunb.) Breit. (P. ternata).

RESULTS

The protoplasts of P. ternata were prepared from plant leaves as the source material by digesting them with the combination of 20 g·l-1 cellulase and 15 g·l-1 macerozyme for 6 h. Based on the screening of PEG concentration, the conditions for PEG-mediated protoplast transformation were improved, and the highest transformation efficiency was found for 40% PEG 4000. Furthermore, we used the subcellular protein localization technique in P. ternata protoplasts to allow further validation of transient expression system.

CONCLUSIONS

We present the method that can be applicable for studying both gene verification and expression in P. ternata protoplasts, thus allowing for engineering the improved varieties of P. ternata through molecular plant breeding techniques. This method can also be widely applicable for analyzing protein interactions, detecting promoter activity, for somatic cell fusion in plant breeding, as well as for other related studies.

Molecular Characterization of Germin-like Protein Genes in Zea mays (ZmGLPs) Using Various In Silico Approaches

Germin (GER) and germin-like proteins (GLPs) play an important role in various plant processes. Zea mays contains 26 germin-like protein genes (ZmGLPs) located on chromosomes 2, 4, and 10; most of which are functionally unexplored. The present study aimed to characterize all ZmGLPs using the latest computational tools. All of them were studied at a physicochemical, subcellular, structural, and functional level, and their expression was predicted in plant development, against biotic and abiotic stresses using various in silico approaches. Overall, ZmGLPs showed greater similarity in their physicochemical properties, domain architecture, and structure, mostly localized in the cytoplasmic or extracellular regions. Phylogenetically, they have a narrow genetic background with a recent history of gene duplication events on chromosome 4. Functional analysis revealed novel enzymatic activities of phosphoglycolate phosphatase, adenosylhomocysteinase, phosphoglycolate phosphatase-like, osmotin/thaumatin-like, and acetohydroxy acid isomeroreductase largely mediated by disulfide bonding. Expression analysis revealed their crucial role in the root, root tips, crown root, elongation and maturation zones, radicle, and cortex with the highest expression being observed during germination and at the maturity levels. Further, ZmGLPs showed strong expression against biotic (Aspergillus flavus, Colletotrichum graminicola, Cercospora zeina, Fusarium verticillioides, and Fusarium virguliforme) while limited expression was noted against abiotic stresses. Concisely, our results provide a platform for additional functional exploration of the ZmGLP genes against various environmental stresses.

Divergent structures and functions of the Cupin proteins in plants

Cupin superfamily proteins have extensive functions. Their members are not only involved in the development of plants but also responded to various stresses. Whereas, the research on the Cupin members has not attracted enough attention. In this article, we summarized the research progress on these family genes in recent years and explored their evolution, structural characteristics, and biological functions. The significance of members of the Cupin family in the development of plant cell walls, roots, leaves, flowers, fruits, and seeds and their role in stress response are highlighted. Simultaneously, the prospective application of Cupin protein in crop enhancement was introduced. Some members can enhance plant growth, development, and resistance to adversity, thereby increasing crop yield. It will be as a foundation for future effective crop research and breeding.

Genome-wide analysis of the GLP gene family and overexpression of GLP1-5-1 to promote lignin accumulation during early somatic embryo development in Dimocarpus longan

Longan (Dimocarpus longan Lour.) is an economically important subtropical fruit tree. Its fruit quality and yield are affected by embryo development. As a plant seed germination marker gene, the germin-like protein (GLP) gene plays an important role in embryo development. However, the mechanism underlying the role of the GLP gene in somatic embryos is still unclear. Therefore, we conducted genome-wide identification of the longan GLP (DlGLP) gene and preliminarily verified the function of DlGLP1-5-1. Thirty-five genes were identified as longan GLP genes and divided into 8 subfamilies. Based on transcriptome data and qRT‒PCR results, DlGLP genes exhibited the highest expression levels in the root, and the expression of most DlGLPs was upregulated during the early somatic embryogenesis (SE) in longan and responded to high temperature stress and 2,4-D treatment; eight DlGLP genes were upregulated under MeJA treatment, and four of them were downregulated under ABA treatment. Subcellular localization showed that DlGLP5-8-2 and DlGLP1-5-1 were located in the cytoplasm and extracellular stroma/chloroplast, respectively. Overexpression of DIGLP1-5-1 in the globular embryos (GEs) of longan promoted the accumulation of lignin and decreased the H₂O₂ content by regulating the activities of ROS-related enzymes. The results provide a reference for the functional analysis of DlGLPs and related research on improving lignin accumulation in the agricultural industry through genetic engineering.

OsGLP3-7 positively regulates rice immune response by activating hydrogen peroxide, jasmonic acid, and phytoalexin metabolic pathways

Although germin-like proteins (GLPs) have been demonstrated to participate in plant biotic stress responses, their specific functions in rice disease resistance are still largely unknown. Here, we report the identification and characterization of OsGLP3-7, a member of the GLP family in rice. Expression of OsGLP3-7 was significantly induced by pathogen infection, jasmonic acid (JA) treatment, and hydrogen peroxide (H₂ O₂ ) treatment. OsGLP3-7 was highly expressed in leaves and sublocalized in the cytoplasm. Overexpression of OsGLP3-7 increased plant resistance to leaf blast, panicle blast, and bacterial blight, whereas disease resistance in OsGLP3-7 RNAi silenced plants was remarkably compromised, suggesting this gene is a positive regulator of disease resistance in rice. Further analysis showed that OsGLP3-7 has superoxide dismutase (SOD) activity and can influence the accumulation of H₂ O₂ in transgenic plants. Many genes involved in JA and phytoalexin biosynthesis were strongly induced, accompanied with elevated levels of JA and phytoalexins in OsGLP3-7-overexpressing plants, while expression of these genes was significantly suppressed and the levels of JA and phytoalexins were reduced in OsGLP3-7 RNAi plants compared with control plants, both before and after pathogen inoculation. Moreover, we showed that OsGLP3-7-dependent phytoalexin accumulation may, at least partially, be attributed to the elevated JA levels observed after pathogen infection. Taken together, our results indicate that OsGLP3-7 positively regulates rice disease resistance by activating JA and phytoalexin metabolic pathways, thus providing novel insights into the disease resistance mechanisms conferred by GLPs in rice.

Decipher the molecular evolution and expression patterns of Cupin family genes in oilseed rape

Cupin proteins are involved in plant growth and development as well as in response to various stresses. Here, a total of 173 Cupin genes were identified in Brassica napus, and their molecular evolution and expression patterns were analyzed. These genes were classified into ten groups. Motif and exon-intron structure indicated a high degree of conservation within each group during evolution. BnaCupins were distributed on 19 chromosomes and their expansion is mainly contributed by whole-genome duplication (WGD) and segmental duplication events. BnaCupins have undergone severe purifying selection during a long evolutionary process. Meanwhile, some positive selection sites were identified. Expression patterns and cis-element analysis indicated that BnaCupins play significant roles in plant growth and stress responses. In addition, the expression levels of some BnCupins were significantly altered when treated with different conditions (cold, salt, drought, IAA, ABA, and 6-BA). Some BnaCupin interacting proteins, such as glycosyl hydrolase5 (GHs5), carbohydrate kinase (CHKs), ATP-dependent 6-phosphofructokinase (ATP-PFK), S-adenosylmethionine synthase (S-MAT), and aldolase class II (ALD II), were identified by the protein-protein interaction network. It will contribute to enriching our knowledge of the Cupin gene family in B. napus and provide a basis for further studies of their functions.

Genome-Wide Identification, Characterization, and Expression Analysis Related to Low-Temperature Stress of the CmGLP Gene Family in Cucumis melo L

Germin-like protein (GLP) participates in plant growth and development and plays an important role in plant stress. In the present study, 22 CmGLPs belonging to five classes were identified in the melon genome. Each member of the CmGLPs family contains a typical Cupin_1 domain. We conducted a genome-wide analysis of the melon GLP gene family characterization. CmGLPs were randomly distributed in the melon chromosomes, with the largest number on chromosome 8, having eight family members. Gene duplication events drive the evolution and expansion of the melon GLP gene family. Based on the phylogenetic tree analysis of GLP proteins in melon, rice, Arabidopsis, and cucumber, it was found that the GLP gene families of different species have diverged in evolution. Based on qRT-PCR results, all members of the CmGLP gene family could be expressed in different tissues of melon. Most CmGLP genes were up-regulated after low-temperature stress. The relative expression of CmGLP2-5 increased by 157.13 times at 48 h after low-temperature treatment. This finding suggests that the CmGLP2-5 might play an important role in low-temperature stress in melon. Furthermore, quantitative dual LUC assays indicated that CmMYB23 and CmWRKY33 can bind the promoter fragment of the CmGLP2-5. These results were helpful in understanding the functional succession and evolution of the melon GLP gene family and further revealed the response of CmGLPs to low-temperature stress in melon.

The Cell Wall Proteome of Marchantia polymorpha Reveals Specificities Compared to Those of Flowering Plants

Primary plant cell walls are composite extracellular structures composed of three major classes of polysaccharides (pectins, hemicelluloses, and cellulose) and of proteins. The cell wall proteins (CWPs) play multiple roles during plant development and in response to environmental stresses by remodeling the polysaccharide and protein networks and acting in signaling processes. To date, the cell wall proteome has been mostly described in flowering plants and has revealed the diversity of the CWP families. In this article, we describe the cell wall proteome of an early divergent plant, Marchantia polymorpha, a Bryophyte which belong to one of the first plant species colonizing lands. It has been possible to identify 410 different CWPs from three development stages of the haploid gametophyte and they could be classified in the same functional classes as the CWPs of flowering plants. This result underlied the ability of M. polymorpha to sustain cell wall dynamics. However, some specificities of the M. polymorpha cell wall proteome could be highlighted, in particular the importance of oxido-reductases such as class III peroxidases and polyphenol oxidases, D-mannose binding lectins, and dirigent-like proteins. These proteins families could be related to the presence of specific compounds in the M. polymorpha cell walls, like mannans or phenolics. This work paves the way for functional studies to unravel the role of CWPs during M. polymorpha development and in response to environmental cues.

The Orthodox Dry Seeds Are Alive: A Clear Example of Desiccation Tolerance

To survive in the dry state, orthodox seeds acquire desiccation tolerance. As maturation progresses, the seeds gradually acquire longevity, which is the total timespan during which the dry seeds remain viable. The desiccation-tolerance mechanism(s) allow seeds to remain dry without losing their ability to germinate. This adaptive trait has played a key role in the evolution of land plants. Understanding the mechanisms for seed survival after desiccation is one of the central goals still unsolved. That is, the cellular protection during dry state and cell repair during rewatering involves a not entirely known molecular network(s). Although desiccation tolerance is retained in seeds of higher plants, resurrection plants belonging to different plant lineages keep the ability to survive desiccation in vegetative tissue. Abscisic acid (ABA) is involved in desiccation tolerance through tight control of the synthesis of unstructured late embryogenesis abundant (LEA) proteins, heat shock thermostable proteins (sHSPs), and non-reducing oligosaccharides. During seed maturation, the progressive loss of water induces the formation of a so-called cellular "glass state". This glassy matrix consists of soluble sugars, which immobilize macromolecules offering protection to membranes and proteins. In this way, the secondary structure of proteins in dry viable seeds is very stable and remains preserved. ABA insensitive-3 (ABI3), highly conserved from bryophytes to Angiosperms, is essential for seed maturation and is the only transcription factor (TF) required for the acquisition of desiccation tolerance and its re-induction in germinated seeds. It is noteworthy that chlorophyll breakdown during the last step of seed maturation is controlled by ABI3. This update contains some current results directly related to the physiological, genetic, and molecular mechanisms involved in survival to desiccation in orthodox seeds. In other words, the mechanisms that facilitate that an orthodox dry seed is a living entity.

Dynamic transcriptome and co-expression analysis suggest the potential roles of small secreted peptides from Tartary buckwheat (Fagopyrum tataricum) in low nitrogen stress response

Small secreted peptides (SSPs) regulate nitrogen (N) response and signaling in plants. Although much progress has been made in understanding the functions of SSPs in N response, very little information is available regarding non-model plants. Tartary buckwheat (Fagopyrum tataricum), a dicotyledonous crop, has a good adaptability to low N (LN) stress; however, little is known regarding the associated mechanisms underlying this adaptation. In this study, 932 putative SSPs were genome-wide characterized in TB genome. Of these SSPs, 233 SSPs were annotated as established SSPs, such as CLE, RALF, PSK, and CEP peptides. The gene expression of 675 putative SSPs was detected in five tissues and 258 SSPs were tissue-specific expressed genes. To analyze the responses of TB SSPs to LN, the dynamic expression analysis of TB roots under LN stress was conducted by RNA-seq. The expression of 378 putative TB SSP genes was detected with diverse expression patterns under LN stress, and some important LN-responsive SSPs were identified. Co-expression analysis suggested SSPs may regulate the adaptability of TB under LN conditions by modulating the expression of the genes involved in N transport and assimilation and IAA signaling. Furthermore, 53 LN stress-responsive RLKs encoding genes were identified and they were predicted as potential SSP receptors. This study expands the repertoire of SSPs in plants and provides useful information for further investigation of the functions of Tartary buckwheat SSPs in LN stress responses.

Germin like protein genes exhibit modular expression during salt and drought stress in elite rice cultivars

BACKGROUND

Germin-like proteins (GLPs) are ubiquitous plant proteins, which play significant role in plant responses against various abiotic stresses. However, the potential functions of GLPs in rice (Oryza sativa) against salt and drought stress are still unclear.

METHODS AND RESULTS

In this study, transcriptional variation of eight OsGLP genes (OsGLP3-6, OsGLP4-1, OsGLP8-4, OsGLP8-7, OsGLP8-10, OsGLP8-11 and OsGLP8-12) was analyzed in leaves and roots of two economically important Indica rice cultivars, KS282 and Super Basmati, under salt and drought stress at early seedling stage. The relative expression analysis from qRT-PCR indicated the highest increase in expression of OsGLP3-6 in leaves and roots of both rice varieties with a significantly higher expression in KS282. Moreover, relative change in expression of OsGLP8-7, OsGLP8-10 and OsGLP8-11 under salt stress and OsGLP8-7 under drought stress was also commonly higher in leaves and roots of KS282 as compared to Super Basmati. Whereas, OsGLP3-7 and OsGLP8-12 after salt stress and OsGLP8-4 and OsGLP8-12 after drought stress were observed with higher relative expression in roots of Super Basmati than KS282. Importantly, the OsGLP3-6 and OsGLP4-1 from chromosome 3 and 4 respectively showed higher expression in leaves whereas most of the OsGLP genes from chromosome 8 exhibited higher expression in roots.

CONCLUSION

Overall, as a result of this comparative analysis, OsGLP genes showed both general and specific expression profiles depending upon a specific rice variety, stress condition as well as tissue type. These results will increase our understanding of role of OsGLP genes in rice crop and provide useful information for the further in-depth research on their regulatory mechanisms in response to these stress conditions.

Characterization of Germin-like Proteins (GLPs) and Their Expression in Response to Abiotic and Biotic Stresses in Cucumber

Germins and germin-like proteins (GLPs) are glycoproteins closely associated with plant development and stress response in the plant kingdom. Here, we carried out genome-wide identification and expression analysis of the GLP gene family in cucumber to study their possible functions. A total of 38 GLP genes were identified in cucumber, which could be mapped to six out of the seven cucumber chromosomes. A phylogenetic analysis of the GLP members from cucumber, Arabidopsis and rice showed that these GLPs could be divided into six groups, and cucumber GLPs in the same group had highly similar conserved motif distribution and gene structure. Gene duplication analysis revealed that six cucumber GLP genes were located in the segmental duplication regions of cucumber chromosomes, while 14 genes were associated with tandem duplications. Tissue expression profiles of cucumber GLP genes showed that many genes were preferentially expressed in specific tissues. In addition, some cucumber GLP genes were differentially expressed under salt, drought and ABA treatments, as well as under DM inoculation. Our results provide important information for the functional identification of GLP genes in the growth, development and stress response of cucumber.

The Cell Wall Proteome of Craterostigma plantagineum Cell Cultures Habituated to Dichlobenil and Isoxaben

The remarkable desiccation tolerance of the vegetative tissues in the resurrection species Craterostigma plantagineum (Hochst.) is favored by its unique cell wall folding mechanism that allows the ordered and reversible shrinking of the cells without damaging neither the cell wall nor the underlying plasma membrane. The ability to withstand extreme drought is also maintained in abscisic acid pre-treated calli, which can be cultured both on solid and in liquid culture media. Cell wall research has greatly advanced, thanks to the use of inhibitors affecting the biosynthesis of e.g., cellulose, since they allowed the identification of the compensatory mechanisms underlying habituation. Considering the innate cell wall plasticity of C. plantagineum, the goal of this investigation was to understand whether habituation to the cellulose biosynthesis inhibitors dichlobenil and isoxaben entailed or not identical mechanisms as known for non-resurrection species and to decipher the cell wall proteome of habituated cells. The results showed that exposure of C. plantagineum calli/cells triggered abnormal phenotypes, as reported in non-resurrection species. Additionally, the data demonstrated that it was possible to habituate Craterostigma cells to dichlobenil and isoxaben and that gene expression and protein abundance did not follow the same trend. Shotgun and gel-based proteomics revealed a common set of proteins induced upon habituation, but also identified candidates solely induced by habituation to one of the two inhibitors. Finally, it is hypothesized that alterations in auxin levels are responsible for the increased abundance of cell wall-related proteins upon habituation.

Transcriptomic, Metabolomic, and Physiological Analyses Reveal That the Culture Temperatures Modulate the Cryotolerance and Embryogenicity of Developing Somatic Embryos in Picea glauca

Cryopreservation is one of the key technologies for the mass propagation of conifers via somatic embryogenesis. Cryotolerance and embryogenecity of conifer somatic embryos (SEs) could be affected by different temperature treatments, for which the underlying mechanisms were unknown. In this study, the developing SEs of Picea glauca obtained their cryotolerance with a survival rate of 100% when cultured on maturation medium at either 23°C for 4 weeks or 4°C for 10 weeks. However, only the embryos that underwent 4°C acclimation remained high embryogenicity, i.e., 91.7% based on cryovials or 29.3% on the plant tissue. Analysis of differentially expressed genes (DEGs) revealed that both 23 and 4°C treatments led to drastic changes in the gene expression, i.e., 21,621 and 14,906 genes, respectively, and the general increase in many oligosaccharides and flavonoids, in addition to the content change of proline (1.9- and 2.3-fold at 23 or 4°C) and gallic acid (6,963- and 22,053-fold). There were 249 significantly different metabolites between the samples of 23 and 4°C treatments and the changing trend of the sorbitol, fatty acids, and monosaccharides differed between these samples. During 4°C-acclimation, the metabolites of the arginine biosynthesis pathway increased between 2.4- and 8.1-fold, and the expression of antioxidant genes was up-regulated significantly. At 4°C, the up-regulated genes were for germ-like proteins, instead of seed storage proteins at 23°C. Concentrations of abscisic acid and jasmonic acid increased up to 2- and 1.5-fold, respectively, in the cold-acclimated embryos. After 10 weeks at 4°C, the embryos stayed at pre-cotyledonary stage with 17.1% less DNA methylation and fewer storage substances than those at 23°C for 4 weeks, which developed cotyledons. This research provides new insights into mechanisms underlying the response of SEs to different culture temperatures and benefits method development for germplasm conservation in conifers.