Induction of multiple shoots from leaf segments, in vitro-flowering and fruiting of a dwarf tomato (Lycopersicon esculentum)

Multiple shoots were induced from leaf explants of Lycopersicon esculentum cultivar MicroTom, within 20-25d, on MS medium supplemented with 8.9 microM benzylaminopurine (BAP)+1.14 microM indole-3-acetic acid (IAA). For rooting, elongated microshoots were excised and transferred onto MS medium supplemented with 4.9 microM indole-3-butyric acid (IBA). Well-developed roots and flower raceme were obtained on d 7 and 13, respectively, upon transfer of the microshoots onto rooting medium. The flowers self-fertilized in vitro and produced mature fruits in additional 15-17d of culture.     

Enhanced salinity stress tolerance in transgenic chilli pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) plants overexpressing the wheat antiporter (<Emphasis Type="Italic">TaNHX2</Emphasis>) gene

Transgenic chilli pepper (Capsicum annuum L.) plants tolerant to salinity stress were produced by introducing the wheat Na⁺/H⁺ antiporter gene (TaNHX2) via Agrobacterium-mediated transformation. Cotyledonary explants were infected with Agrobacterium tumefaciens strain LBA4404 harboring a binary vector pBin438 that contains a wheat antiporter (TaNHX2) gene driven by the double CaMV 35S promoter and NPT II gene as a selectable marker. PCR and semiquantitative RT-PCR analysis confirmed that the TaNHX2 gene had been integrated and expressed in the T₁ generation of transgenic pepper plants as compared to the non-transformed plants. Southern blot analysis further verified the integration and presence of TaNHX2 gene in the genome of chilli pepper plants. Biochemical assays of these transgenic plants revealed enhanced levels of proline, chlorophyll, superoxide dismutase, ascorbate peroxidase, relative water content, and reduced levels of hydrogen peroxide (H₂O₂), malondialdehyde compared to wild-type plants under salt stress conditions. The present investigation clearly showed that overexpression of the TaNHX2 gene enhanced salt stress tolerance in transgenic chilli pepper plants.     

Reconciliation of classification systems defining molecular subtypes of colorectal cancer

Recently we published two independent studies describing novel gene expression-based classifications of colorectal cancer (CRC). Notably, each study stratified CRC into a different number of subtypes: one reported 3 subtypes, whereas the second highlighted 5. Given that each ascribed clinical significance, distinctive biology, and therapeutic prognosis to the different subtypes, we sought to reconcile this apparent incongruity in subtype stratification of CRC, and to interrelate the results. To do so, we each evaluated the other’s data sets and analytical methods and discovered that the subtypes and their classifiers are, in fact, clearly related to each other; indeed, the 5 subtype outcomes can be coalesced into the same three. In addition to presenting this clarification, we briefly discuss how both classification methods can be viewed within the broader literature on CRC subtypes, and potentially applied.     

Somatic embryogenesis from leaf cultures of potato

An efficient procedure has been developed for inducing somatic embryogenesis from leaf cultures of potato cv. Jyothi. Leaf sections were initially cultured on 2,4-dichlorophenoxyacetic acid (2,4-D) + benzyladenine (BA) and -naphthaleneacetic acid (NAA) + BA supplemented Murashige and Skoog (MS) media. Nodular embryogenic callus developed from the cut ends of explants on media containing 2,4-D and BA, whereas compact callus developed on media containing NAA and BA. The explants with primary callus were subsequently moved onto MS media containing zeatin and/or gibberellic acid (GA₃) and BA. Treatment with zeatin (22.8 M) and BA (10.0 M) resulted in the induction of the highest number of somatic embryos directly from meristematic centres produced on the nodular tissue. Embryo induction and maturation took place on this medium. The cotyledonary stage embryos developed into complete plantlets on hormone-free MS medium. A distinct feature of this study is the induction of somatic embryogenesis in leaf cultures of potato which has not been reported previously.     

High-frequency plant regeneration and genetic homogeneity assessment of regenerants by molecular markers in turmeric (Curcuma longa L.)

In Vitro Cellular & Developmental Biology - Plant - A highly efficient and reproducible in vitro plant regeneration method has been developed from shoot bud, half-shoot, and shoot slice...     

A rapid and efficient method for in vitro shoot organogenesis and production of transgenic Bacopa monnieri L. mediated by Agrobacterium tumefaciens

Efficient shoot regeneration and Agrobacterium-mediated genetic transformation systems were developed for Bacopa monnieri L. (Scrophulariaceae), a plant well known for its medicinal properties. Leaf explants were cultured on Murashige and Skoog (MS) medium with different concentrations of 6-benzylaminopurine (BAP), and in combination with either indole-3-acetic acid (IAA) or napthalene-3-acetic acid. A combination of BAP (17.80 μM) and IAA (2.28 μM) maximized shoot initiation (85.2 ± 2.43) with greatest shoot length (2.8 ± 0.22), and was obtained directly from leaf explants without an intervening callus phase. Leaf segments from in vitro grown plants were co-cultivated with Agrobacterium tumefaciens LBA4404 harboring pCAMBIA1301 with ?-glucuronidase (uidA) and hygromycin phosphotransferase (hpt) genes. The co-cultivated explants were transferred to selective shoot induction and elongation medium. The elongated hygromycin-resistant shoots were subsequently rooted on MS medium supplemented with 4.9 μM indole-3-butyric acid and 25 mg/l hygromycin (SSRM). Successful transformation was confirmed by monitoring histochemical GUS activity during shoot elongation and PCR analyses using uidA- and hpt-specific primers. Integration of hpt into the genome of transgenic plants was also verified by Southern blot analysis. The highest transformation efficiency achieved was 70.6%, with an average of 10.4 ± 0.15 transgenic plantlets per explant using the present transformation system. Therefore, these highly efficient and rapid regeneration and transformation systems create significant potential for engineering of B. monnieri with a view to detailed biomolecular analyses or for further enhancement of its medicinal properties.     

EMS-induced streptomycin resistance in Solanum melongena

Streptomycin-resistant mutations were induced in Solanum melongena by exposing seeds to ethyl methane sulphonate (EMS). Seed mutagenesis resulted in a high frequency of chlorophyll-deficient mutations and a low frequency of resistant shoots, both of which retained their resistance on subsequent testing. Reciprocal crosses between streptomycin-resistant and -sensitive plants showed a non-Mendelian transmission of the resistance trait. Streptomycin resistance is the first selectable and maternally inherited organelle marker described in brinjal.