Promotion and Upregulation of a Plasma Membrane Proton-ATPase Strategy: Principles and Applications

Plasma membrane proton-ATPase (PM H+-ATPase) is a primary H+ transporter that consumes ATP in vivo and is a limiting factor in the blue light-induced stomatal opening signaling pathway. It was recently reported that manipulation of PM H+-ATPase in stomatal guard cells and other tissues greatly improved leaf photosynthesis and plant growth. In this report, we review and discuss the function of PM H+-ATPase in the context of the promotion and upregulation H+-ATPase strategy, including associated principles pertaining to enhanced stomatal opening, environmental plasticity, and potential applications in crops and nanotechnology. We highlight the great potential of the promotion and upregulation H+-ATPase strategy, and explain why it may be applied in many crops in the future.

Cytoanatomical marker traits of the ploidy level in fruit and berry crops

For use in breeding work, the methods of complex accelerated cytological diagnosis of genotypes of fruit and berry crops with an altered ploidy level were optimized. The proposed diagnostic method was tested on polyploids of the genus Malus, Fragaria, Ribes, Rubus, rowan-pear hybrids and is recommended for wide scientific and practical application in the plant breeding and cytology. The effectiveness of this method is ensured by its availability and reliable statistical differences in accounting parameters. In a comprehensive cytological diagnosis of forms of fruit and berry crops with an increased level of ploidy, it is proposed to first study the morphoanatomical traits (sizes and proportions of stomatal guard cells, the number of chloroplasts in them, the diameter of pollen grains). This will significantly reduce the time of laboratory analysis and field assessment by deleting forms with unchanged indicator values.

Identification of Genes Preferentially Expressed in Stomatal Guard Cells of Arabidopsis thaliana and Involvement of the Aluminum-Activated Malate Transporter 6 Vacuolar Malate Channel in Stomatal Opening

Stomatal guard cells (GCs) are highly specialized cells that respond to various stimuli, such as blue light (BL) and abscisic acid, for the regulation of stomatal aperture. Many signaling components that are involved in the stomatal movement are preferentially expressed in GCs. In this study, we identified four new such genes in addition to an aluminum-activated malate transporter, ALMT6, and GDSL lipase, Occlusion of Stomatal Pore 1 (OSP1), based on the expression analysis using public resources, reverse transcription PCR, and promoter-driven β-glucuronidase assays. Some null mutants of GC-specific genes evidenced altered stomatal movement. We further investigated the role played by ALMT6, a vacuolar malate channel, in stomatal opening. Epidermal strips from an ALMT6-null mutant exhibited defective stomatal opening induced by BL and fusicoccin, a strong plasma membrane H+-ATPase activator. The deficiency was enhanced when the assay buffer [Cl–] was low, suggesting that malate and/or Cl– facilitate efficient opening. The results indicate that the GC-specific genes are frequently involved in stomatal movement. Further detailed analyses of the hitherto uncharacterized GC-specific genes will provide new insights into stomatal regulation.

Changes In Ploidy Affect Vascular Allometry And Hydraulic Function In Trees

The enucleated vascular elements of the xylem and the phloem offer an excellent system to test the effect of ploidy on plant function because variation in vascular geometry has a direct influence on transport efficiency. However, evaluations of conduit sizes in polyploid plants have remained elusive, most remarkably in woody species. We used a combination of molecular, physiological, and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees. Tetraploids exhibited larger chloroplasts, mesophyll cells, and stomatal guard cells, resulting in higher leaf elastic modulus and lower dehydration rates despite the high water potentials of both ploidies in the field. Both the xylem and the phloem displayed a scaling of conduits with ploidy, revealing attenuated hydraulic resistance in tetraploids. Conspicuous wall hygroscopic moieties in the cells involved in processes of transpiration and transport advocates a role in volumetric adjustments due to turgor change in polyploids, which, together with the enlargement of organelles, cells, and tissues that are critical for water and photoassimilate transport at long distances, imply major physiological novelties of polyploidy.

Heat-Induced Oxidation of the Nuclei and Cytosol

The concept that heat stress (HS) causes a large accumulation of reactive oxygen species (ROS) is widely accepted. However, the intracellular compartmentation of ROS accumulation has been poorly characterized. We therefore used redox-sensitive green fluorescent protein (roGFP2) to provide compartment-specific information on heat-induced redox changes of the nuclei and cytosol of Arabidopsis leaf epidermal and stomatal guard cells. We show that HS causes a large increase in the degree of oxidation of both compartments, causing large shifts in the glutathione redox potentials of the cells. Heat-induced increases in the levels of the marker transcripts, heat shock protein (HSP)101, and ascorbate peroxidase (APX)2 were maximal after 15 min of the onset of the heat treatment. RNAseq analysis of the transcript profiles of the control and heat-treated seedlings revealed large changes in transcripts encoding HSPs, mitochondrial proteins, transcription factors, and other nuclear localized components. We conclude that HS causes extensive oxidation of the nucleus as well as the cytosol. We propose that the heat-induced changes in the nuclear redox state are central to both genetic and epigenetic control of plant responses to HS.

Genome-wide Identification and Functional Analysis of the H3 Gene Family in Cotton

Background: Histones are major components of chromatin, which is a nucleosome structure associated with chromosome segregation, DNA packaging and transcriptional regulation. Histone H3 is encoded by many genes in most eukaryotic species, but little information is known about the Histone H3 gene family in cotton.Results: In this study, we identified and analyzed the evolution and expression of histone H3 gene family in cotton. First, 34 G. hirsutum genes were identified belonging to the H3 gene family which were divided into four subclasses: CENH3, H3.1, H3.3 and H3-like. Among these H3.1 subclass contained the highest number of genes (22 members) followed by H3.3 subclass (9 members). In addition, there were18 and 16 H3 genes identified in G. arboretum and G. raimondii, respectively. Furthermore, we conducted conserved sequence analysis of H3 proteins, and found that the four amino acids signature including A31F41S87A90 for H3.1 and T31Y41H87L90 for H3.3 could be used to discriminate H3.1 from H3.3. The expression of H3 gene family varied in different tissues and developmental stages of G. hirsutum, where H3.1 subclass genes play a critical role in pistil development. By virus-induced gene silencing of GhCENH3 (Gh_D07G1382) gene, the size of leaf got smaller with pYL156-CENH3 than that with pYL156 in TM-1. Whereas, the number of the stomata in the leaf epidermis and number of chloroplasts in the leaf stomatal guard cells by pYL156-CENH3 was more than that by pYL156 and pYL156-PDS.Conclusions: Four sub-classes (CENH3, H3.1, H3.3 and H3-like) of H3 gene family were highly conserved in cotton during the rapid phase of evolution among which CENH3 is necessary for leaf growth. These findings are useful for providing further insights into cotton biology and breeding.

Single-Cell Resolution of Lineage Trajectories in the Arabidopsis Stomatal Lineage and Developing Leaf

SUMMARYDynamic cell states underlie flexible developmental programs, such as with the stomatal lineage of the Arabidopsis epidermis. Initial stages of the lineage feature asynchronous and indeterminate divisions modulated by environmental cues, enabling cell fate flexibility to generate the requisite density and pattern of stomata for a given environment. It remains unclear, however, how flexibility of cell fates is controlled. Here, we uncovered distinct models of cell state differentiation within Arabidopsis leaf tissue by leveraging single-cell transcriptomics and molecular genetics. Our findings resolved underlying heterogeneity within cell states of the flexible epidermal stomatal lineage, which appear to exist along a continuum, with progressive cell specification. Beyond the early stages of the lineage, we discovered that the core transcriptional regulator SPEECHLESS is required for cell fate commitment to yield stomatal guard cells. Overall, our work has refined the stomatal lineage paradigm and uncovered progressive cell state decisions along lineage trajectories in developing leaves.

Predicting the unexpected in stomatal gas exchange: not just an open-and-shut case

Plant membrane transport, like transport across all eukaryotic membranes, is highly non-linear and leads to interactions with characteristics so complex that they defy intuitive understanding. The physiological behaviour of stomatal guard cells is a case in point in which, for example, mutations expected to influence stomatal closing have profound effects on stomatal opening and manipulating transport across the vacuolar membrane affects the plasma membrane. Quantitative mathematical modelling is an essential tool in these circumstances, both to integrate the knowledge of each transport process and to understand the consequences of their manipulation in vivo. Here, we outline the OnGuard modelling environment and its use as a guide to predicting the emergent properties arising from the interactions between non-linear transport processes. We summarise some of the recent insights arising from OnGuard, demonstrate its utility in interpreting stomatal behaviour, and suggest ways in which the OnGuard environment may facilitate ‘reverse-engineering’ of stomata to improve water use efficiency and carbon assimilation.

Assessment of the Ploidy Level Diversity by Chloroplast Counts in Stomatal Guard Cells of Potato (Solanum tuberosum L.) Mutants

Aims: Potato (Solanum tuberosum L.) is the most important staple food in the world and plays an important role in food and nutritional security. Induced mutation generates variation within potato germplasm to widen the genetic base for breeding purposes. Polyploidy modifies both the genotype and phenotype of an organism, generating diverse changes that consequently transform the potato production. Potato has chromosomes with different ploidy levels which can be determined by counting chloroplasts in stomatal guard cells. Study Design: The study was carried out in completely randomized block design. Place and Duration of Study: Department of Biotechnology, University of Eldoret, between February 2015 and July 2016. Methodology: The study involved 163 potato mutants developed from three commercially grown Kenyan potato varieties; Asante, Mpya, and Sherekea irradiated using gamma rays from 60Co source under different dose rates. Three middle leaves of greenhouse-grown plants were randomly selected for chloroplast counts in ten pairs of stomata guard cells on the lower surface of the leaf. Data on the number of chloroplast counts per mutant was calculated as a percentage of the parents or control and descriptive analysis. Results: The results indicate that the number of ploidy level distribution was decreasing in diploids and triploids and were increasing in tetraploids from M1V1, M1V2 to M1V3 in all the potato mutant populations. Conclusion: This shows that mutation induction generates genetic variations from which desired mutants may be selected based on the appropriate breeding strategies.