Lateral Meristems Research Articles

Type of Explant Affects In Vitro Development and Multiplication Success of the Rare Halophyte Plant Honckenya Peploides L. Ehrh.

The sea sandwort—Honckenya peploides (L.) Ehrh. is—a rare halophilous plant growing on dunes and is an endangered species on the Polish coast. It contributes to the stabilization of volatile sandy substrate, facilitating the colonization of other species. The present study determined the reaction of two types of explant: apical shoot fragments and fragments from a lower portion of the shoot. Apical shoot fragments were used to propagate and root sea sandwort plants due to the positive impact on the development of shoots and roots. Regardless of the plant growth regulators applied in the medium, the lateral meristems on the explants from the lower parts of the shoot stopped growing, and then yellowed and died out. Apical fragments of shoots developed higher and more numerous shoots and longer and more numerous roots than explants, which were fragments collected from lower parts of shoots. The findings indicated that propagation should be conducted on Murashige and Skoog medium with the addition of 1 mg∙dm−3 kinetin, whereas shoots with their apical fragments should be rooted with the addition of 1.5 mg∙dm−3 1-naphthaleneacetic acid. The results also showed that the addition of NaCl at concentrations of 25 and 50 mM did not restrict their growth, thereby indicating the tolerance of the plant to soil salinity. However, an increase in the concentration of NaCl in the medium to 75 mM restricted the development of plants, and the shoots were lower and roots were shorter and less numerous.

Gibberellin disturbs the balance of endogenesis hormones and inhibits adventitious root development of Pseudostellaria heterophylla through regulating gene expression related to hormone synthesis.

The adventitious roots of some plants will develop into tuberous roots which are widely used in many traditional Chinese medicines, including Pseudostellaria heterophylla. If adventitious root development is inhibited, the yield of Chinese medicinal materials will be reduced. Gibberellic acid is an important phytohormone that promotes plant growth and increases the resistance to drought, flood or disease. However, the effects of gibberellic acid on adventitious roots of Pseudostellaria heterophylla are not clear. Here, we reports GA3 suppressed adventitious root development of Pseudostellaria heterophylla by disturbing the balance of endogenesis hormones. By detecting the contents of various endogenous hormones, we found that the development of adventitious roots negatively correlated with the content of CA3 in tuberous roots. Exogenous GA3 treatment decreased the diameter of adventitious roots, but increased the length of adventitious roots of Pseudostellaria heterophylla. In contrast, blocking the biosynthesis of GA3 suppressed stem growth and promoted the xylem of tuberous roots development. Moreover, exogenous GA3 treatment resulted in imbalance of endogenesis hormones by regulating their synthesis-related genes expression in xylem of tuberous roots. These results suggest GA3 broke the established distribution of hormones by regulating synthesis, transport and biological activation of hormones to activate the apical meristem and suppress lateral meristem. Regulating GA3 signaling during adventitious roots development would be one of the possible ways to increase the yield of P. heterophylla.

Effect of thidiazuron and monochromatic light on shoot development in vitro culture of Polygonum cuspidatum Sieb et Zucc

Polygonum cuspidatum Sieb. et Zucc, a medicinal plant, contains many phenolic compounds such as resveratrol. It has antioxidant, antibacterial, anti-cancer, HIV, and neuron protective properties. In this study, stem segments having an auxiliary bud were cultured in vitro on MS medium supplemented with TDZ at 0.1 mg/L for obtaining the highest number of shoots (8–9 shoots/cluster after eight weeks). The bud shoots were originated from the differentiation in the periphery of the lateral meristem. After eight weeks, the shoots cultured under the monochromatic light showed that the plant height, fresh and dry weight was higher than those grown under the fluorescent light at the same intensity of 50 µmol photon/m2/sec. Blue LED reduced the number of shoots/cluster, and respiration intensity of the inoculum compared to the red LED or fluorescent light conditions. However, after eight weeks, the total sugar and phenolic content in leaves and stems, as well as the resveratrol content of shoots under blue light, were always higher than under red LED or fluorescent light. Moreover, when samples were exposed under the one-week blue light condition at a double intensity (100 µmol photon/m2/sec), the shoot clusters growing under blue LED also had a remarkably high total phenolic content and significantly high resveratrol levels compared to the two other treatments. The roles of endogenous growth regulators in shoot clusters under different lighting conditions were also analyzed and discussed.

AfLFY, a LEAFY homolog in Argyranthemum frutescens, controls flowering time and leaf development

Flowering is important for plant propagation and survival, and it is also closely related to human life. Identifying the molecular mechanisms underlying flower development is essential for plant improvement and breeding. Flower development is a complex physiological process that is regulated by multiple genes. LFY genes play important roles in the floral meristem transition and act as crucial integrators in regulating the floral gene network. Argyranthemum frutescens is an ornamental species cultivated for floral displays, yet little is known about molecular mechanisms driving its flower development. In this study, the LEAFY gene homologue, AfLFY, was identified and cloned from A. frutescens, and its role and expression patterns were characterized. Two distinct copies of AfLFY were found in the A. frutescens genome and both sequences contained a 1248 bp open reading frame that encoded 415 amino acids. The putative protein sequences have a typical LFY family domain. In addition, AfLFY was expressed at the highest levels in young leaves of the vegetative stage and in the shoot apical bud meristem of the reproductive stage. Phylogenetic analysis showed that AfLFY was most closely related to DFL from Chrysanthemum lavandulifolium. Subcellular localization studies revealed that AfLFY localized to the nucleus. Heterologous expression of AfLFY in transgenic tobacco plants shortened its period of vegetative growth, converted the lateral meristems into terminal flowers and promoted precocious flowering. In addition, transgenic plants exhibited obvious morphological changes in leaf shape. qRT-PCR analysis indicated that the expression levels genes related to flowering, FT, SOC1, and AP1 were significantly upregulated in AfLFY transgenic plants. Our findings suggested that the AfLFY gene plays a vital role in promoting flowering and leaf development in A. frutescens. These results laid a foundation for us to understand the mechanism of AfLFY in regulation flowering, and the results will be helpful in improving A. frutescens through molecular breeding.

MiR156a-targeted SBP-Box transcription factor SlSPL13 regulates inflorescence morphogenesis by directly activating SFT in tomato.

The inflorescences and lateral branches of higher plants are generated by lateral meristems. The structure of the inflorescence has a direct effect on fruit yield in tomato (Solanum lycopersicum). We previously demonstrated that miR156a plays important roles in determining the structures of the inflorescences and lateral branches in tomato by suppressing the expression of the SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) transcription factor gene family. However, information on regulatory pathways associated with inflorescence morphogenesis is still lacking. In this study, we demonstrate that SPL13 is the major SPL involved in miR156a‐regulated tomato inflorescence structure determination and lateral branch production. Suppressing the expression of SPL13 in tomato increases the number of inflorescences on vegetative branches and lateral branches, decreases the number of flowers and fruit, and reduces fruit size and yield. Genetic and biochemical evidence indicate that SPL13 controls inflorescence development by positively regulating the expression of the tomato inflorescence‐associated gene SINGLE FLOWER TRUSS (SFT) by directly binding to its promoter region. Thus, our findings provide a major advance to our understanding of the miR156a‐SlSPL‐based mechanism that regulates plant architecture and yield in tomato.

Multifeature analyses of vascular cambial cells reveal longevity mechanisms in old Ginkgo biloba trees.

Aging is a universal property of multicellular organisms. Although some tree species can live for centuries or millennia, the molecular and metabolic mechanisms underlying their longevity are unclear. To address this, we investigated age-related changes in the vascular cambium from 15- to 667-y-old Ginkgo biloba trees. The ring width decreased sharply during the first 100 to 200 y, with only a slight change after 200 y of age, accompanied by decreasing numbers of cambial cell layers. In contrast, average basal area increment (BAI) continuously increased with aging, showing that the lateral meristem can retain indeterminacy in old trees. The indole-3-acetic acid (IAA) concentration in cambial cells decreased with age, whereas the content of abscisic acid (ABA) increased significantly. In addition, cell division-, cell expansion-, and differentiation-related genes exhibited significantly lower expression in old trees, especially miR166 and HD-ZIP III interaction networks involved in cambial activity. Disease resistance-associated genes retained high expression in old trees, along with genes associated with synthesis of preformed protective secondary metabolites. Comprehensive evaluation of the expression of genes related to autophagy, senescence, and age-related miRNAs, together with analysis of leaf photosynthetic efficiencies and seed germination rates, demonstrated that the old trees are still in a healthy, mature state, and senescence is not manifested at the whole-plant level. Taken together, our results reveal that long-lived trees have evolved compensatory mechanisms to maintain a balance between growth and aging processes. This involves continued cambial divisions, high expression of resistance-associated genes, and continued synthetic capacity of preformed protective secondary metabolites.

The Striking Flower-in-Flower Phenotype of Arabidopsis thaliana Nossen (No-0) is Caused by a Novel LEAFY Allele.

The transition to reproduction is a crucial step in the life cycle of any organism. In Arabidopsis thaliana the establishment of reproductive growth can be divided into two phases: Firstly, cauline leaves with axillary meristems are formed and internode elongation begins. Secondly, lateral meristems develop into flowers with defined organs. Floral shoots are usually determinate and suppress the development of lateral shoots. Here, we describe a transposon insertion mutant in the Nossen accession with defects in floral development and growth. Most strikingly is the outgrowth of stems from the axillary bracts of the primary flower carrying secondary flowers. Therefore, we named this mutant flower-in-flower (fif). However, the transposon insertion in the annotated gene is not the cause for the fif phenotype. By means of classical and genome sequencing-based mapping, the mutation responsible for the fif phenotype was found to be in the LEAFY gene. The mutation, a G-to-A exchange in the second exon of LEAFY, creates a novel lfy allele and results in a cysteine-to-tyrosine exchange in the α1-helix of LEAFY’s DNA-binding domain. This exchange abolishes target DNA-binding, whereas subcellular localization and homomerization are not affected. To explain the strong fif phenotype against these molecular findings, several hypotheses are discussed.

Mapping a Transcriptome-Guided Arabidopsis SAM Interactome.

The advent of multi-OMICS approaches has a significant impact on the investigation of biological processes occurring in plants. RNA-SEQ, cellular proteomics, and metabolomics have added a considerable ease in studying the dynamics of stem cell niches. New cell sorting approaches coupled with the labeling of stem cell population specific marker genes are highly instrumental in enriching distinct cellular populations for various types of analysis. One more promising field of OMICS is the mapping of cellular interactomes. The plant stem cells research is barely profited from this newly emerging field of OMICS. Generation of stem cell/niche-specific interactome is a time-consuming and labor-intensive task. Here, we describe a method on how to assemble a SAM-based interactome after using the available generic Arabidopsis interactomes. To define the context of SAM in a generic interactome, we used SAM cell population transcriptome datasets. Our step-by-step protocol can easily be adopted for other stem cell niches such as RAM and lateral meristems keeping in view the availability of transcriptome datasets for cellular populations of these niches.

CsTFL1 inhibits determinate growth and terminal flower formation through interaction with CsNOT2a in cucumber.

ABSTRACTCucumber (Cucumis sativus L.) is an important vegetable crop that carries on vegetative growth and reproductive growth simultaneously. Indeterminate growth is favourable for fresh market under protected environments, whereas determinate growth is preferred for pickling cucumber in the once-over mechanical harvest system. The genetic basis of determinacy is largely unknown in cucumber. In this study, map-based cloning of the de locus showed that the determinate growth habit is caused by a non-synonymous SNP in CsTFL1. CsTFL1 is expressed in the subapical regions of the shoot apical meristem, lateral meristem and young stems. Ectopic expression of CsTFL1 rescued the terminal flower phenotype in the Arabidopsis tfl1-11 mutant and delayed flowering in wild-type Arabidopsis. Knockdown of CsTFL1 resulted in determinate growth and formation of terminal flowers in cucumber. Biochemical analyses indicated that CsTFL1 interacts with a homolog of the miRNA biogenesis gene CsNOT2a; CsNOT2a interacts with FDP. Cucumber CsFT directly interacts with CsNOT2a and CsFD, and CsFD interacts with two 14-3-3 proteins. These data suggest that CsTFL1 competes with CsFT for interaction with CsNOT2a-CsFDP to inhibit determinate growth and terminal flower formation in cucumber.

Wheat VRN1, FUL2 and FUL3 play critical and redundant roles in spikelet development and spike determinacy.

ABSTRACTThe spikelet is the basic unit of the grass inflorescence. In this study, we show that wheat MADS-box genes VRN1, FUL2 and FUL3 play critical and redundant roles in spikelet and spike development, and also affect flowering time and plant height. In the vrn1ful2ful3-null triple mutant, the inflorescence meristem formed a normal double-ridge structure, but then the lateral meristems generated vegetative tillers subtended by leaves instead of spikelets. These results suggest an essential role of these three genes in the fate of the upper spikelet ridge and the suppression of the lower leaf ridge. Inflorescence meristems of vrn1ful2ful3-null and vrn1ful2-null remained indeterminate and single vrn1-null and ful2-null mutants showed delayed formation of the terminal spikelet and increased number of spikelets per spike. Moreover, the ful2-null mutant showed more florets per spikelet, which together with a higher number of spikelets, resulted in a significant increase in the number of grains per spike in the field. Our results suggest that a better understanding of the mechanisms underlying wheat spikelet and spike development can inform future strategies to improve grain yield in wheat.

Cryopreservation of grapevine (Vitis spp.) shoot tips from growth chamber-sourced plants and histological observations

Many genebanks rely on cryopreservation as a method to preserve vulnerable field collections of vegetatively propagated crops. Effective cryopreservation procedures have been identified for Vitis; however, they usually use in vitro plantlets as the shoot tip source materials. It is costly to establish Vitis collections in vitro prior to cryopreservation. We sought to determine if growth chamber derived Vitis plants could serve as the source of shoot tips for cryopreservation. Nodal sections from growth chamber derived plants were surface-disinfected and placed in tissue culture on pre-treatment medium for 2 weeks. Uniform apical shoot tips (1 mm) were first obtained from the nodal sections and then precultured for 3 days on medium containing 0.3 M sucrose, salicylic acid, glutathione (reduced form), ascorbic acid and plant preservative mixture. Half-strength PVS2 was applied for 30 min at 22 °C, prior to full-strength PVS2 treatment at 0 °C. Cryopreserved shoot tips had the highest average regrowth of 50 and 55 % without and with cold-acclimation followed with a full-strength PVS2 exposure duration of 40 and 30 min at 0 °C, respectively. This cryopreservation protocol achieved high percentages of regrowth in V. vinifera 'Chardonnay' and 'Riesling' and V. hybrid 'Oppenheim'. Histological observations revealed that shoot tips from growth chamber plants had apical as well as multiple lateral meristems that survived LN immersion. The preservation of multiple meristems in each shoot tip may increase the capacity of shoot tip regeneration in cryopreserved Vitis that originates from ex vitro sources. The high percentage of regrowth after shoot tip cryopreservation using Vitis shoot tips derived from growth chamber source plants suggest that it may be possible to cryopreserve Vitis shoot tips without first introducing each accession into tissue culture.

Origin, activity and environmental acclimation of stem secondary tissues of the polar willow (Salix polaris) in high-Arctic Spitsbergen

High Arctic is an intensively explored region in relation to predicted global warming. Its long-term impact is analysed in dwarf-shrubs, such as a widely distributed and pioneering species Salix polaris (polar willow). Understanding the functioning of lateral meristems in these dwarf-shrubs is however limited, affecting interpretation of the data. The presented study focused on the formation and anatomy of the derived secondary tissues in the stems of S. polaris from polar habitats. The entire branches of the polar willow were collected in five vegetation types of tundra located in SW Spitsbergen (Svalbard) and analysed on the series of transverse and longitudinal sections. Our analyses showed that the periderm developed in two or three-year old stems as the secondary protective tissue, and that the multiple epidermis, typical of many willow species, was not formed in S. polaris. The secondary xylem in the polar willow stems showed considerable differences in diameter and length of vessel elements within a single stem. Importantly, the size of the vessel elements differed also depending on the tundra vegetation type. Our findings suggest that the soil moisture was a main factor determining the size of vessels, and that their size was not correlated to the nitrogen supply. Our study thus demonstrated the usefulness of different anatomical features of wood, in above-ground organs, in High Arctic research.

Tissue-specific study across the stem reveals the chemistry and transcriptome dynamics of birch bark.

Tree bark is a highly specialized array of tissues that plays important roles in plant protection and development. Bark tissues develop from two lateral meristems; the phellogen (cork cambium) produces the outermost stem-environment barrier called the periderm, while the vascular cambium contributes with phloem tissues. Although bark is diverse in terms of tissues, functions and species, it remains understudied at higher resolution. We dissected the stem of silver birch (Betula pendula) into eight major tissue types, and characterized these by a combined transcriptomics and metabolomics approach. We further analyzed the varying bark types within the Betulaceae family. The two meristems had a distinct contribution to the stem transcriptomic landscape. Furthermore, inter- and intraspecies analyses illustrated the unique molecular profile of the phellem. We identified multiple tissue-specific metabolic pathways, such as the mevalonate/betulin biosynthesis pathway, that displayed differential evolution within the Betulaceae. A detailed analysis of suberin and betulin biosynthesis pathways identified a set of underlying regulators and highlighted the important role of local, small-scale gene duplication events in the evolution of metabolic pathways. This work reveals the transcriptome and metabolic diversity among bark tissues and provides insights to its development and evolution, as well as its biotechnological applications.

Histochemical Study of Xylem Cells in In Vitro Culture of Iris sibirica L.

In this study, lignin content data are presented for annual regenerant Iris sibirica plants, comparable to those in six-year-old intact plants. The structure of the shoots of Iris sibirica grown on artificial nutrient media was studied by the histochemical method. Features of the formation of the xylem in Iris sibirica on artificial nutrient media were revealed. Regenerants very quickly developed a complex system consisting of vascular bundles containing sieve tubes, vessels and tracheids, and hydrocyte systems. Hydrocytes of Iris sibirica were tracheids with lignified thickening, but, in contrast to tracheids and vessels of xylem (they are formed based on procambium or cambium—special lateral primary or secondary meristem), hydrocytes differentiated from the cells of permanent tissues (like phellogen), which probably possessed meristematic activity at the time of differentiation. In Iris sibirica hydrocytes covered the vascular bundle by the thick layer and strung along it up to a certain height. High lignin content in young regenerant Iris sibirica plants was due to the formation of the dense tissue from lignified tracheal elements. The study of the differentiation of xylem elements under controlled conditions can serve as a model for our understanding of wood formation processes.

Simulation of tree growth for three almond cultivars with contrasting architecture with the L-ALMOND model

The L-PEACH and L-ALMOND models use L-systems to simulate the architectural development and carbohydrate dynamics (assimilation, transport, distribution, storage and remobilization) of growing peach and almond trees, respectively. The models were able to successfully simulate tree growth and development and produce realistic estimates of tree size, structure and productivity over several years after planting, but always only for a specific cultivar. We here show how L-ALMOND can be adapted to simulate the architectural growth of three cultivars (‘Nonpareil’, ‘Aldrich’, and ‘Winters’) differing in tree architecture after three steps for each cultivar: i) inclusion of specific shoot architectures for six types of shoots (watersprouts, long, medium-long, medium, medium-short, and small shoots). Branching patterns and flowering occurrence for each type of shoot were previously assessed by developing hidden semi-Markov statistical models based on field research. Spur morphology was the same. Very different patterns emerged of sylleptic shoot production from lateral meristems on watersprouts, long, and medium-long shoots. ‘Aldrich’ and ‘Winters’ produced many more sylleptic shoots than ‘Nonpareil’. No sylleptic shoot growth appeared from medium, medium-short, and small shoots in any cultivar; ii) definition of the type of shoot derived from a sylleptic shoot. In ‘Aldrich’ and ‘Winters’ most sylleptic shoots were spurs and short shoots, respectively, while in ‘Nonpareil’ their length varied widely (spurs, small, medium-short, and medium shoots); and iii) adjustment of a parameter to modify shoot bending to simulate differences in growth habit observed in the field. ‘Aldrich’ was more erect than ‘Winters’ and ‘Nonpareil’. After modifications, L-ALMOND 3-dimensional tree simulations were similar to actual pictures of field trees, demonstrating how different shoot architectures result in different tree architectures over time, and especially the role that sylleptic shoot production plays in determining final tree architecture in almond.

Sector analysis reveals patterns of cambium differentiation in poplar stems.

We used sector analysis to study cambium development and dynamics and to test whether fundamental developmental and functional differences exist between cambial initials as true 'stem cells' and more differentiated mother cells. In many higher plants, a cylindrical lateral meristem, the vascular cambium, forms along the plant axis. Most notably in stems of perennial tree species, this meristem gives rise to xylem (wood) towards the inside of the trunk and phloem (bark) towards the outside. As such, the vascular cambium is responsible for the production of most of the planet's forest biomass, significantly contributing to the global carbon cycle. Using the bacterial uidA reporter gene in Agrobacterium-based in vivo stem transformation experiments in poplar trees, we created 379 cambium sectors that originated from the transformation of individual cells. Results from our analysis of sector frequency and patterns are consistent with the poplar cambium featuring a single layer of true cambial initials (being able to divide both anti- and periclinally). We show that initials are frequently lost from the cambium, that such cell loss rarely occurs at mother cell level, that phloem and xylem differentiation are controlled independently, and that the frequency of mother cell replenishment is not pre-determined.

Evolutionary, interaction and expression analysis of floral meristem identity genes in inflorescence induction of the second crop in two-crop-a-year grape culture system

The fruitfulness of grapevines (Vitis viniferaL.) is determined to a large extent by the differentiation of uncommitted meristems, especially in the second-crop production of some varieties, where the intermediate of inflorescence and tendril accounts for a significant proportion in two-crop-a-year grape culture system. The differentiation of uncommitted lateral meristem was reported to be regulated by a network, whose backbone was composed of several floral meristem identity genes. In the present study, the phylogenetics of grape floral meristem identity genes with their orthologues in other species, and their conserved domain and interaction networks were analysed. In addition, the effects of chlormequat chloride and pinching treatments on the expression profiles of floral meristem identity genes and content of gibberellic acid (GAs) and zeatin riboside (ZR), as well as the ratio of ZR/GAs in buds that were used to produce the second crop, and the ratio of inflorescence induction of the second crop were studied in 'Summer Black'. The present results showed that floral meristem identity genes of grape and their orthologues in one or more among Malus domastic, Citrus sinensis, heobroma cacaoT, Nicotiana tabacum, Solanum lycopersicum and Glycine hirsutum, probably originated from a common ancestor. Interaction networks of six grape-floral meristem identity genes indicated that the inflorescence induction and floral development were regulated by one more complex network, and expression profiles of genes that involved in this network could be affected by each other. Expression profiles of eight floral meristem identity genes were affected by chlormequat chloride and pinching treatments, and higher expression levels of FT, TFL1A and TFL1B, as well as lower expression levels of LFY from 3 days before full bloom to 11 days after full bloom were thought to play important roles in promoting the formation of inflorescence primordial of the second crop, and higher expression levels of CAL A, SOC1 and TFL1A at 18 days after full bloom (DAF) could promote the development of inflorescence primordial. In addition, lower ratio of ZR/GAs at 3 days before full bloom and 4 days after full bloom could promote the formation of uncommitted lateral meristems in chlormequat chloride and pinching-treated plants, and higher ratio at 11 days after full bloom was the main reason for the formation of more inflorescences after chlormequat chloride treatment.

ITRAQ-based quantitative proteomic analysis reveals the lateral meristem developmental mechanism for branched spike development in tetraploid wheat (Triticum turgidum L.)

BackgroundSpike architecture mutants in tetraploid wheat (Triticum turgidum L., 2n = 28, AABB) have a distinct morphology, with parts of the rachis node producing lateral meristems that develop into ramified spikelete (RSs) or four-rowed spikelete (FRSs). The genetic basis of RSs and FRSs has been analyzed, but little is known about the underlying developmental mechanisms of the lateral meristem. We used isobaric tags for relative and absolute quantitation (iTRAQ) to perform a quantitative proteomic analysis of immature spikes harvested from tetraploid near-isogenic lines of wheat with normal spikelete (NSs), FRSs, and RSs and investigated the molecular mechanisms of lateral meristem differentiation and development. This work provides valuable insight into the underlying functions of the lateral meristem and how it can produce differences in the branching of tetraploid wheat spikes.ResultsUsing an iTRAQ-based shotgun quantitation approach, 104 differential abundance proteins (DAPs) with < 1% false discovery rate (FDR) and a 1.5-fold change (> 1.50 or < 0.67) were identified by comparing FRS with NS and RS with NS genotypes. To determine the functions of the proteins, 38 co-expressed DAPs from the two groups were annotated using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analytical tools. We discovered that proteins involved in “post-embryonic development” and “metabolic pathways” such as carbohydrate and nitrogen metabolism could be used to construct a developmentally associated network. Additionally, 6 out of 38 DAPs in the network were analyzed using quantitative real-time polymerase chain reaction, and the correlation coefficient between proteomics and qRT-PCR was 0.7005. These key genes and proteins were closely scrutinized and discussed.ConclusionsHere, we predicted that DAPs involved in “post-embryonic development” and “metabolic pathways” may be responsible for the spikelete architecture changes in FRS and RS. Furthermore, we discussed the potential function of several vital DAPs from GO and KEGG analyses that were closely related to histone modification, ubiquitin-mediated protein degradation, transcription factors, carbohydrate and nitrogen metabolism and heat shock proteins (HSPs). This work provides valuable insight into the underlying functions of the lateral meristem in the branching of tetraploid wheat spikes.

Suppression of DELLA signaling induces procambial cell formation in culture.

The post-embryonic growth of plants requires the activities of apical meristems and lateral meristems. In the meristems, self-proliferation and differentiation of stem cells is tightly modulated by plant hormone signaling networks and specific transcription factors. Despite extensive studies on stem cell maintenance in plants, the mechanism by which stem cells are initially established is largely unknown. Vascular stem cells consisting of procambial/cambial cells give rise to xylem and phloem cells. In this study, we analyzed the establishment of procambial cells using the invitro culture system VISUAL, in which mesophyll cells rapidly differentiate into xylem tracheary elements and phloem sieve elements via procambial cells. We found that procambial cell formation in VISUAL is initiated by light, which can be replaced by application of gibberellin (GA). Gibberellin was able to promote procambial cell formation through degradation of DELLA, whereas light did not elevate the endogenous GA content. Indeed, light in combination with bikinin reduced the accumulation of DELLA protein in VISUAL. Consistently, overexpression of a constitutively active DELLA protein repressed vascular cell differentiation even under light. These combined results suggest that DELLA signaling suppresses procambial cell formation during vascular development in VISUAL.

Gametophyte morphology of Acrostichum aureum and A. danaeifolium (Pteridaceae)

Acrostichum is a pantropical genus and has four species, two of which occur in the Neotropics, A. aureum and A. danaeifolium. In Mexico, A. danaeifolium grows further in land wet soils and is much more common than A. aureum, which is typically found in brackish or saline habitats near the coast, and is restricted to coastal saline mangrove communities. The purpose of this paper was to describe and compare the morphogenesis of the sexual phase of A. aureum and A. danaeifolium for systematic purposes. For this, spores of each species were sown in Petri dishes with agar, previously enriched with sterilized Thompson's medium. To avoid contamination and dehydration, the dishes were kept in transparent plastic bags under laboratory conditions. For the micro-morphological observation with SEM, the gametophyte development phases were fixed in FAA with 0.8 % sucrose for 24 h. Photomicrographs of spores, development stages of gametophytes and young sporophytes were observed with scanning electron microscope Jeol JSM5310-LV. Our results showed that the spores of both species are triletes, globose and positive photoblastic. Germination is Vittaria-type; the germinate filaments are short and uniseriate (5 to 7 cells), and prothallial development is Ceratopteris-type. The adult gametophytes of both species have asymmetrical wings. Adult gametophytes in culture are cordiform-spatulate. Antheridia have a broad basal cell, an annular cell, and an asymmetric opercular cell. Archegonia have short necks and four triangular cells at the mouth of the neck. The first leaf of the sporophyte is lobed, with dichotomous veins and anomocytic stomata. The gemmae are formed in adult gametophytes in both species. The development of the gametophyte of A. aureum, A. danaeifolium and A. speciosum share many similarities such as the development of a lateral meristem, asymmetric nature of the mature prothallus, lack of hairs on the prothallus, and undivided asymmetrical opercular antheridia morphology. The genus Acrostichum is the sister group of Ceratopteris, another genus of aquatic ferns; they differ in the antheridium morphology, Acrostichum has an asymmetric opercular cell and Ceratopteris shows an undivided cap cell, but the notable difference is the sporophyte morphology.