The management of extracellular ice by petioles of frost-resistant herbaceous plants. (1/14)

BACKGROUND AND AIMS: Some frost-tolerant herbaceous plants droop and wilt during frost events and recover turgor and posture on thawing. It has long been known that when plant tissues freeze, extracellular ice forms. Distributions of ice and water in frost-frozen and recovered petioles of Trifolium repens and Escholschzia californica were visualized. METHODS: Petioles of intact plants were cryo-fixed, planed to smooth transverse faces, and examined in a cryo-SEM. KEY RESULTS: With frost-freezing, parenchyma tissues shrank to approx. one-third of their natural volume with marked cytorrhysis of the cells, and massive blocks of extracellular icicles grew under the epidermis (poppy) or epidermis and subepidermis (clover), leaving these layers intact but widely separated from the parenchyma except at specially structured anchorages overlying vascular bundles. On thawing, the extracellular ice was reabsorbed by the expanding parenchyma, and surface tissues again contacted the internal tissues at weak junctions (termed faults). These movements of water into and from the fault zones occurred repeatedly at each frost/thaw event, and are interpreted to explain the turgor changes that led to wilting and recovery. Ice accumulations at tri-cellular junctions with intercellular spaces distended these spaces into large cylinders, especially large in clover. Xylem vessels of frozen petioles were nearly all free of gas; in thawed petioles up to 20 % of vessels were gas-filled. CONCLUSIONS: The occurrence of faults and anchorages may be expected to be widespread in frost-tolerant herbaceous plants, as a strategy accommodating extracellular ice deposits which prevent intracellular freezing and consequent membrane disruption, as well as preventing gross structural damage to the organs. The developmental processes that lead to this differentiation of separation of sheets of cells firmly cemented at determined regions at their edges, and their physiological consequences, will repay detailed investigation.  (+info)

The Galpha protein controls a pH-dependent signal path to the induction of phytoalexin biosynthesis in Eschscholzia californica. (2/14)

The function of a Galpha protein in the elicitation of phytoalexin (benzophenanthridine) biosynthesis was characterized in cultured cells of California poppy (Eschscholzia californica). Both the decrease of Galpha content via antisense transformation and the expression of recombinant anti-Galpha single-chain antibodies strongly impaired the induction of alkaloid biosynthesis by low elicitor concentrations. All transgenic cell types were deficient in two elicitor-triggered early signal events: activation of phospholipase A2 (PLA2) and efflux of vacuolar protons. The lacking H+ efflux could be restored (1) by adding lysophosphatidylcholine (LPC), a product of PLA2 activity, to vacuoles in situ and (2) by exposing intact cells to isotonic, near-neutral HEPES buffers. The latter treatment induced alkaloid biosynthesis in the absence of elicitor and in Galpha-deficient cells. We conclude that Galpha mediates the stimulation of PLA2 by low elicitor concentrations and that the resulting peak of LPC initiates a transient efflux of vacuolar protons. In this way, an acidic peak of the cytoplasmic pH is generated that causes the expression of enzymes of phytoalexin production independent of the hypersensitive response.  (+info)

Highly efficient virus-induced gene silencing (VIGS) in California poppy (Eschscholzia californica): an evaluation of VIGS as a strategy to obtain functional data from non-model plants. (3/14)

BACKGROUND AND AIMS: Eschscholzia californica (California poppy) is an emerging model plant for 'evo-devo' studies from the basal eudicot clade of Papaveraceae. California poppy has a relatively small genome, a short life cycle and, most importantly, it is amenable for transformation. However, since this transformation protocol is time consuming, virus-induced gene silencing (VIGS) was evaluated as a fast method to obtain functional data for California poppy genes. METHODS: Commercially available California poppy plants were infiltrated with Agrobacterium tumefaciens carrying the tobacco rattle virus plasmids pTRV1 and pTRV2. pTRV2 contained part of the eschscholzia Phytoene Desaturase (EcPDS) gene whose loss of function results in photobleaching of the green parts of the plant and in a lack of floral coloration. The degree and duration of these symptoms was evaluated for vegetative rosettes and plants in flower. KEY RESULTS: It is shown that VIGS is able to effectively down-regulate the EcPDS gene in eschscholzia. Various degrees of silencing were observed starting <2 weeks after infiltration with Agrobacterium tumefaciens in 92 % of the plants. Tissue with silencing symptoms also showed complete or strong reduction of EcPDS transcripts. Strong silencing resulted in almost completely white petals, fruits, shoots and leaves. Plants with a strong degree of silencing will eventually die off; however, others are able to produce EcPDS gene product even after a strong initial silencing and will recover. Silencing was found to be not always systemic, but was often restricted to certain organs or parts of organs. CONCLUSIONS: VIGS is an effective, fast and transient method to down-regulate gene expression in eschscholzia. It serves well to detect prominent phenotypes which may become obvious even if some target gene transcript remains in the plant tissue. However, subtle phenotypes will be more difficult to detect, as extremely strong silencing effects occur in <10 % of all flowers from infected plants.  (+info)

Differential induction of protein expression and benzophenanthridine alkaloid accumulation in Eschscholtzia californica suspension cultures by methyl jasmonate and yeast extract. (4/14)

Methyl jasmonate (MJ) and yeast extract (YE) induce protein expression and benzophenanthridine alkaloid accumulation in Eschscholtzia californica suspension cell cultures. One hundred microM MJ primarily induced dihydrosanguinarine 509.0+/-7.4 mg/l); 0.2 g/l YE induced sanguinarine (146.8+/- 3.8 mg/l) and an unknown compound. These results occur because dihydrobenzophenanthridine oxidase (DHBO) is induced by YE and not by MJ. YE and chitin (CHI) had similar effects on sanguinarine production and DHBO expression. Differential induction of secondary metabolites was shown in E. californica suspension cultures and the expression of proteins confirmed the metabolite results. Furthermore, treatment by various oligosaccharides helped us to understand the elicitation effect of YE in signal transduction pathways.  (+info)

Structural and mechanistic studies reveal the functional role of bicovalent flavinylation in berberine bridge enzyme. (5/14)

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Comparison of next generation sequencing technologies for transcriptome characterization. (6/14)

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Structure and mechanism of sanguinarine reductase, an enzyme of alkaloid detoxification. (7/14)

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Inheritance and epistasis of loci influencing carotenoid content in petal and pollen color variants of california Poppy (Eschscholzia californica Cham.). (8/14)

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