Symbiotic nitrogen fixation boosts legume growth and production in nitrogen-poor soils. It has long been assumed that fixed nitrogen increases reproductive success, but until now, the regulatory mechanism was unknown. Here, we report a symbiotic flowering pathway that couples symbiotic and nutrient signals to the flowering induction pathway in legumes. We show that the symbiotic microRNA–microRNA172c (miR172c) and fixed nitrogen systemically and synergistically convey symbiotic and nutritional cues from roots to leaves to promote soybean ( Glycine max ) flowering. The combinations of symbiotic miR172c and local miR172c elicited by fixed nitrogen and development in leaves activate florigen-encoding FLOWERING LOCUS T ( FT ) homologs ( GmFT2a/5a ) by repressing TARGET OF EAT1-like 4a ( GmTOE4a ). Thus, FTs trigger reproductive development, which allows legumes to survive and reproduce under low-nitrogen conditions.

Calcium (Ca2+) signals are decoded by the Ca2+-sensor protein calmodulin (CaM) and are transduced to Ca2+/CaM-binding transcription factors to directly regulate gene expression necessary for acclimation responses in plants. The molecular mechanisms of Ca2+/CaM signal transduction processes and their functional significance remains enigmatic. Here we report a novel Ca2+/CaM signal transduction mechanism that allosterically regulates DNA-binding activity of GT2-LIKE 1 (GTL1), a transrepressor of STOMATAL DENSITY AND DISTRIBUTION 1 (SDD1), to repress stomatal development in response to water stress. We demonstrated that Ca2+/CaM interaction with the 2nd helix of the GTL1 N-terminal trihelix DNA-binding domain (GTL1N) destabilizes a hydrophobic core of GTL1N and allosterically inhibits 3rd helix docking to the SDD1 promoter, leading to osmotic stress-induced Ca2+/CaM-dependent activation (de-repression) of SDD1 expression. This resulted in GTL1-dependent repression of stomatal development in response to water-deficit stress. Together, our results demonstrate that a Ca2+/CaM-regulated transcriptional switch on a trihelix transrepressor directly transduces osmotic stress to repress stomatal development to improve plant water-use efficiency as an acclimation response.

A cell line of Mcetiana tabacum L, var. Wisconsin 38 was selectcd (S-1O cells) which is capable of grewth in medium containing 10 g literi NaCl. The fresh and dry weights of S-1O cells at stationary phase in medium containing 1O g liter-i NaCl were about 60 and 1OO%respectively,ofthatofS-rOcellsgrownwithoutNaCl. Whencellsnormallymaintained in the absence of the salt (S-O cells) were transferred to medium containing 10 g liter-i NaCl, they underwent a 14-day lag period before growth could be detected and they reached stationary phase 36 days after inoculation compared to 14 days for S-10

Gibberellins (GAs) are phytohormones that regulate plant height and flowering time in plants. Plants with reduced GA or disrupted in GA signaling exhibit a dwarf phenotype. DELLA proteins are transcriptional repressors that attenuate GA-mediated promotion of plant growth. Alleles in which the eponymous DELLA motif in these proteins is disrupted result in constitutive repression of GA signaling and a dominantly inherited dwarf phenotype. We found that the dwarf Helianthus annuus (sunflower) cultivar Sunspot is hyposensitive to GA 3 as compared with the tall cultivar Mammoth Grey. Sequencing of the HaDella1 gene indicates that ‘Sunspot’ has a single nucleotide polymorphism resulting in a missense mutation in the DELLA motif as compared with ‘Mammoth Grey’ and the reference sequence. Helianthus annuus has five genes encoding DELLA proteins, including HaDella1 . We propose that the DELLA motif alteration in the HaDella1 gene results in a dominant mutation in ‘Sunspot’ and is the cause of its dwarf phenotype.

Crop yield reduction as a consequence of increasingly severe climatic events threatens global food security. Genetic loci that ensure productivity in challenging environments exist within the germplasm of crops, their wild relatives and species that are adapted to extreme environments. Selective breeding for the combination of beneficial loci in germplasm has improved yields in diverse environments throughout the history of agriculture. An effective new paradigm is the targeted identification of specific genetic determinants of stress adaptation that have evolved in nature and their precise introgression into elite varieties. These loci are often associated with distinct regulation or function, duplication and/or neofunctionalization of genes that maintain plant homeostasis.

Soil and water salinity substantially constrain crop and biomass production. Research over the last two plus decades, facilitated by advances in molecular genetics and biotechnology, and with genetic model systems, has identified genes involved in salt acclimation or adaptation and linked these to critical mechanisms and processes. A case in point is present understanding of critical transport determinants that facilitate intra- and intercellular Na+ homeostasis of plants in saline environments predominated by NaCl. Pumps in the plasma membrane (H+-ATPase), and the tonoplast (H+-ATPase) and H+ pyrophosphatases (AVP1) generate proton electrochemical gradients necessary to energize Na+ efflux to the apoplast and influx into vacuoles, respectively. The plasma membrane Na+/H+ antiporter SOS1 is responsible for apoplastic efflux, and NHX type Na+/H+ antiporters for vacuolar and endosomal compartmentalization. Ca-ext(2+) reduces passive intracellular Na+ influx cells by decreasing Na+ transport through high affinity K+ uptake systems and what are presumed to be nonselective cation channels, and activating, through the SOS signal pathway, the SOS1 plasma membrane Na+/H+ antiporter. Moreover, there is greater understanding about how cellular transport systems functionally integrate to facilitate tissue and organismal Na+ homeostasis. Notable in this process are HKT1 Na+ transporters, which regulate Na+ loading into the root xylem, limiting flux to and accumulation in the shoot. This review will summarize ion transport systems that facilitate plant Na+ homeostasis. Halophyte and glycophyte salinity responses and transport determinant function are compared and contrasted. The potential of halophytes as genetic resources for unique alleles or loci of transport protein genes and transcriptional and post-transcriptional regulation of transport protein function are discussed in the context of crop salt tolerance. (C) 2013 Elsevier B.V. All rights reserved.

CYCLIN H;1 regulates reactive oxygen species-dependent but abscisic acid-independent inhibition of blue light-induced stomatal aperture required for drought stress responses. Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE Ds (CDKDs) phosphorylate the C-terminal domain of the largest subunit of RNA polymerase II. Arabidopsis CYCLIN H;1 (CYCH;1) interacts with and activates CDKDs; however, the physiological function of CYCH;1 has not been determined. Here, we report that CYCH;1, which is localized to the nucleus, positively regulates blue light-induced stomatal opening. Reduced-function cych;1 RNA interference (cych;1 RNAi) plants exhibited a drought tolerance phenotype. CYCH;1 is predominantly expressed in guard cells, and its expression was substantially down-regulated by dehydration. Transpiration of intact leaves was reduced in cych;1 RNAi plants compared with the wild-type control in light but not in darkness. CYCH;1 down-regulation impaired blue light-induced stomatal opening but did not affect guard cell development or abscisic acid-mediated stomatal closure. Microarray and real-time polymerase chain reaction analyses indicated that CYCH;1 did not regulate the expression of abscisic acid-responsive genes or light-induced stomatal opening signaling determinants, such as MYB60, MYB61, Hypersensitive to red and blue1, and Protein phosphatase7. CYCH;1 down-regulation induced the expression of redox homeostasis genes, such as LIPOXYGENASE3 (LOX3), LOX4, ARABIDOPSIS GLUTATHIONE PEROXIDASE 7 (ATGPX7), EARLY LIGHT-INDUCIBLE PROTEIN1 (ELIP1), and ELIP2, and increased hydrogen peroxide production in guard cells. Furthermore, loss-of-function mutations in CDKD;2 or CDKD;3 did not affect responsiveness to drought stress, suggesting that CYCH;1 regulates the drought stress response in a CDKD-independent manner. We propose that CYCH;1 regulates blue light-mediated stomatal opening by controlling reactive oxygen species homeostasis.

Female gametophyte is the multicellular haploid structure that can produce embryo and endosperm after fertilization, which has become an attractive model system for investigating molecular mechanisms in nuclei migration, cell specification, cell-to-cell communication and many other processes. Previous reports found that the small ubiquitin-like modifier (SUMO) E3 ligase, SIZ1, participated in many processes depending on particular target substrates and suppression of salicylic acid (SA) accumulation. Here, we report that SIZ1 mediates the reproductive process. SIZ1 showed enhanced expression in female organs, but was not detected in the anther or pollen. A defect in the siz1-2 maternal source resulted in reduced seed-set regardless of high SA concentration within the plant. Moreover, aniline blue staining and scanning electron microscopy revealed that funicular and micropylar pollen tube guidance was arrested in siz1-2 plants. Some of the embryo sacs of ovules in siz1-2 were also disrupted quickly after stage FG7. There was no significant affects of the siz1-2 mutation on expression of genes involved in female gametophyte development- or pollen tube guidance in ovaries. Together, our results suggest that SIZ1 sustains the stability and normal function of the mature female gametophyte which is necessary for pollen tube guidance.

SummaryTranspiration and gas exchange occur through stomata. Thus, the control of stomatal aperture is important for the efficiency and regulation of water use, and for the response to drought. Here, we demonstrate that SIZ1‐mediated endogenous salicylic acid (SA) accumulation plays an important role in stomatal closure and drought tolerance. siz1 reduced stomatal apertures. The reduced stomatal apertures of siz1 were inhibited by the application of peroxidase inhibitors, salicylhydroxamic acid and azide, which inhibits SA‐dependent reactive oxygen species (ROS) production, but not by an NADPH oxidase inhibitor, diphenyl iodonium chloride, which inhibits ABA‐dependent ROS production. Furthermore, the introduction of nahG into siz1, which reduces SA accumulation, restored stomatal opening. Stomatal closure is generally induced by water deficit. The siz1 mutation caused drought tolerance, whereas nahG siz1 suppressed the tolerant phenotype. Drought stresses also induced expression of SA‐responsive genes, such as PR1 and PR2. Furthermore, other SA‐accumulating mutants, cpr5 and acd6, exhibited stomatal closure and drought tolerance, and nahG suppressed the phenotype of cpr5 and acd6, as did siz1 and nahG siz1. Together, these results suggest that SIZ1 negatively affects stomatal closure and drought tolerance through the accumulation of SA.

As the oldest and largest human intervention in nature, the science of agriculture is one of the most intensely studied practices. From manipulation of plant gene structure to the use of plants for bioenergy, biotechnology interventions in plant and agricultural science have been rapidly developing over the past ten years with immense forward leaps on an annual basis. This book begins by laying the foundations for plant biotechnology by outlining the biological aspects including gene structure and expression, and the basic procedures in plant biotechnology of genomics, metabolomics, transcriptomics and proteomics. It then focuses on a discussion of the impacts of biotechnology on plant breeding technologies and germplasm sustainability. The role of biotechnology in the improvement of agricultural traits, production of industrial products and pharmaceuticals as well as biomaterials and biomass provide a historical perspective and a look to the future. This title includes sections addressing intellectual property rights and sociological and food safety issues that round out the holistic discussion of this important topic. It also includes specific emphasis on the inter-relationships between basic plant biotechnologies and applied agricultural applications, and the way they contribute to each other. It provides an updated review of the major plant biotechnology procedures and techniques, their impact on novel agricultural development and crop plant improvement. It takes a broad view of the topic with discussions of practices in many countries.

Diminishing global fresh water availability has focused research to elucidate mechanisms of water use in poplar, an economically important species. A GT-2 family trihelix transcription factor that is a determinant of water use efficiency (WUE), PtaGTL1 (GT-2 like 1), was identified in Populus tremula × P. alba (clone 717-IB4). Like other GT-2 family members, PtaGTL1 contains both N- and C-terminal trihelix DNA binding domains. PtaGTL1 expression, driven by the Arabidopsis thaliana AtGTL1 promoter, suppressed the higher WUE and drought tolerance phenotypes of an Arabidopsis GTL1 loss-of-function mutation (gtl1-4). Genetic suppression of gtl1-4 was associated with increased stomatal density due to repression of Arabidopsis STOMATAL DENSITY AND DISTRIBUTION1 (AtSDD1), a negative regulator of stomatal development. Electrophoretic mobility shift assays (EMSA) indicated that a PtaGTL1 C-terminal DNA trihelix binding fragment (PtaGTL1-C) interacted with an AtSDD1 promoter fragment containing the GT3 box (GGTAAA), and this GT3 box was necessary for binding. PtaGTL1-C also interacted with a PtaSDD1 promoter fragment via the GT2 box (GGTAAT). PtaSDD1 encodes a protein with 60% primary sequence identity with AtSDD1. In vitro molecular interaction assays were used to determine that Ca2+-loaded calmodulin (CaM) binds to PtaGTL1-C, which was predicted to have a CaM-interaction domain in the first helix of the C-terminal trihelix DNA binding domain. These results indicate that, in Arabidopsis and poplar, GTL1 and SDD1 are fundamental components of stomatal lineage. In addition, PtaGTL1 is a Ca2+-CaM binding protein, which infers a mechanism by which environmental stimuli can induce Ca2+ signatures that would modulate stomatal development and regulate plant water use.

A stoma (pl. stomata) is the pore formed by two guard cells found predominantly in the leaf epidermis. Plants control stomatal aperture (opening and closing) and/or number (density) to regulate carbon dioxide (CO2) uptake and water loss (transpiration), which is necessary to optimize plant growth, development, and fitness in response to various environmental conditions. Recently, we identified Arabidopsis GT2-LIKE 1 (GTL1) as a transcriptional repressor of STOMATAL DENSITY AND DISTRIBUTION 1 (SDD1), a negative regulator of stomatal density. GTL1 directly interacts with the SDD1 promoter regulating stomatal density, transpiration, and water use efficiency (WUE). Here we discuss potential GTL1 orthologs in other plant species.

ICE1, a MYC-type transcription factor, has an important role in the induction of CBF3/DREB1A for regulation of cold signaling and tolerance. Here we reveal that serine 403 of ICE1 is involved in regulating the transactivation and stability of the ICE1 protein. Substitution of serine 403 by alanine enhanced the transactivational activity of ICE1 in Arabidopsis protoplasts. Over-expression of ICE1(S403A) conferred more freezing tolerance than ICE1(WT) in Arabidopsis, and the expression of cold-regulated genes such as CBF3/DREB1A, COR47 and KIN1 was enhanced in plants over-expressing ICE1(S403A). Furthermore, the ICE1(S403A) protein level was not changed after cold treatment, whereas the ICE1(WT) protein level was reduced. Interestingly, polyubiquitylation of the ICE1(S403A) protein in vivo was apparently blocked. These results demonstrate that serine 403 of ICE1 has roles in both transactivation and cold-induced degradation of ICE1 via the ubiquitin/26S proteasome pathway, suggesting that serine 403 is a key residue for the attenuation of cold-stress responses by HOS1-mediated degradation of ICE1.

The post-translational conjugation of small ubiquitin-related modifiers (SUMOs) to other proteins is involved in regulation of many processes in eukaryotic development; although its role in plant development is beginning to be dissected. Previously, we demonstrated that the siz1 mutant, which is impaired in SUMO E3 ligase, showed a dwarf-like shoot phenotype with accumulation of salicylic acid (SA), and the expression of nahG, a bacterial salicylate hydroxylase that catabolizes SA, in siz1 reduced the SA level and suppressed dwarfism. Herein, we provide evidence that the SIZ1 gene controls cell division and elongation through regulation of the SA level. Mature siz1-2 and siz1-3 plants exhibited a dwarf-like shoot phenotype that is attributable to decreased leaf cell volume and number relative to the wild type. Cell division and expansion defects caused by siz1 were also suppressed by the expression of nahG. Expression of XTH8 and XTH31, encoding xyloglucan endotransglycosylase/hydrolase, which are thought to facilitate leaf cell expansion, was down-regulated in siz1 leaves. However, reduced XTH8 and XTH31 expression in siz1 plants was restored in nahG siz1-2 plants. These results indicate that SIZ1 regulates cell growth and plant development with regulation of SA accumulation. Also, XTH8 and XTH31 genes may be responsible for reduced leaf cell expansion.