147 research outputs found
Regeneration and genetic transformation in cowpea
Over the last three decades, sporadic efforts have been made to develop regeneration
and transformation systems in cowpea (Vigna unguiculata L. Walp). This paper
reviews the progress made to date, including highlights of culture media and
explants used for regeneration and chimeric gene constructs employed in transformations.
Progress has been slow, mainly due to limited resources, since very few
laboratories have been involved. There is an urgent need for more focused and
consistent efforts to develop genotype, and tissue-culture dependent and independent
approaches for obtaining stable genetic transformation in cowpea
Use of somatic embryogenesis as a vehicle for cotton transformation
Cotton has been aptly described as the prosperity plant owing to its unrivalled economic importance as
a source of feedstock, food and oil, as well as raw material for diverse industrial applications, ranging
from textile and footwear to automobiles, energy, medical and pharmaceutical. As such, over 180
million people of the world depend on its production for livelihood. However, cotton production is
grossly hampered, and has long been peaked in many regions where it is being grown. Without
prejudice to the genetic improvement already made by conventional breeding with respect to yield and
quality over the years, genetic transformation is arguably the last recourse for further development of
cotton, especially with respect to the prevailing production constraints of insect pests, weeds,
environmental stresses and diseases. This review therefore focuses on the use of somatic
embryogenesis as a vehicle for cotton genetic transformation. It indeed attempts to overview the
challenges of cotton transformation with respect to narrow genetic base coupled with the recalcitrant
nature of the crop species, as well as the research success achieved so far. It then discusses the
underlying mechanisms of somatic embryogenesis as well as the current constraints and various
strategies being used to overcome them; all with the aim of motivating interest groups to initiate
research activities in cotton biotechnology and to strive for its optimization for further genetic
improvement
Irregular deposition of cell wall polymers resulting from defective cellulose synthase complexes
The crystalline cellulose microfibril is formed by
the spontaneous association of about 36 β-D-glucan
chains, which are simultaneously synthesised by a large
membrane-localised multi-enzyme cellulose synthase
complex. Antisense technology has been previously
employed separately on two of the constituent cellulose
synthase catalytic subunits (CesA) of the complex in
potato (Solanum tuberosum), namely CesA2 and CesA4,
to generate potato tuber cell walls with reduced cellulose
content. Genetic crossing of two transgenic potato lines
csr2-1 and csr4-8 was carried out to investigate the
effects of two defective CesAs in the same genetic
background, with respect to cellulose deposition in the
potato tuber cell walls. It was striking to observe, through
fluorescence microscopy with calcofluor white, a strong
fluorescence in the cell corners and less prominent and
uneven fluorescence around the cells of the csr2 tubers
as compared to others. It was also noted that these
phenotypes were not pronounced in the csr2/csr4 double
transformants as expected
Endogenous levels of reducing sugars, free amino acids and phenols during various stages of in vitro culture of cotton (Gossypium Spp.)
Somatic embryogenesis is widely preferred as the regeneration route for in vitro studies in cotton.
However, the regeneration efficiency through this approach is low; a problem that is believed to be as a result
of the biochemical properties of the plant. The objective of this study was to investigate possible relationships
between three biochemical factors (reducing sugars, phenols, and free amino acids) and somatic
embryogenesis. In vitro cultures of the different embryogenic and non-embryogenic cultivals were established.
The levels of reducing sugars, phenols and free amino acids were determined at different developmental stages
of the cultures. Higher levels of reducing sugars and lower level of phenol were observed in embryogenic
cultivars compared to their non-embryogenic counterparts. There was a general increase in the levels of free
amino acids, which decreased with time in the highly embryogenic cultivars, whereas the levels remained high
in the poorly embryogenic and non-embryogenic cultivars. The higher content of phenols and free amino acids
may be implicated in the poor somatic embryogenic response. The data show that there are factors that may
serve as markers of somatic embryogenesis in cotton, which need to be empirically determined for any
particular cultivar chosen for genetic improvement through embryogenesis
Molecular analysis and phenotype characterization of the progeny of two antisense potato plants
Two transgenic potato lines csr2-1 and csr4-8, containing two different antisense constructs, csr2 and
csr4, respectively, were crossed to investigate the possibility of achieving double transformants with
combined effects of the two antisense transgenes on plant phenotypes and cellulose deposition.
Molecular analysis revealed an expected segregation ratio of 1:1:1:1 of the four classes. Phenotype
characterization revealed that offspring containing either one or both transgenes produced more tubers
than the control plants but individual tubers were mostly smaller and had lesser weight than the control
tubers
Exciting Times for Cowpea Genetic Transformation Research
Cowpea represents a major food crop for the poor in Asia and especially in Africa.
However, its production is constrained principally by insect pests as well as diseases. Attempts to
improve cowpea insect resistance have not yielded significant result till date. This paper reviews
biotechnological approaches that have been employed to transfer foreign genes into cowpea with a
view to conferring desirable traits on it. The recent advances made in generating cowpea transformants
with stable inheritance of trangenes by the progenies heralds exciting times for the genetic
transformation research on this erstwhile recalcitrant food crop. As such, this genetic transformation
approach could be used to transfer insect resistance traits to the crop species
STUDIES ON KOLA TISSUE CULTURE II: Effect of plant growth regulators on callus induction
Callus induction was studied on leaf and single node cutting explants obtained from Cola nitida (Vent.) Schott and Endlicher seedlings. Callus was induced successfully from cut surfaces (periphery) ofyoung leaves in vitro on the medium supplemented with 0.5-5.0 mgl-1 naphtheneacetic
acid (NAA), combined with 0.23 mgt- I 6-benzyl-aminopurine (BAP) and on medium supplemented with 0.2-0.6 mgl-1 BAP, combined with 1.0 mgl-1 NAA. Successful callus induction was al so obtained from the buds of single nodal explants cultured on MS medium supplemented with 0.1-1 .0
mgl-1 NAA, combined with 2.3 mgl-1 BAP
Expression of the C-terminal family 22 carbohydratebinding module of xylanase 10B of Clostridium themocellum in tobacco plant
Carbohydrate-binding modules have been shown to alter plant cell wall structural architecture. Hence,
they have the potential application of being used to engineer the plant to produce tailor-made natural
fibers in the cell wall. The Clostridium thermocellum xylanase, Xyn10B, contains two CBMs that belong
to family 22 (CBM22). The C-terminal CBM22-2 of the glycoside hydrolase (GH) 10 had been
characterized to interact with xylan, a major hemicellulosic component in the secondary cell wall of
plants. In this work, the expression of the CBM22-2 in transgenic tobacco plants was evaluated.
Histological examinations of the transgenic stems did not reveal marked cell wall phenotype. In
addition, there were no observable changes in the height or the appearance of the transgenic plants
expressing the CBM22-2 module. The results indicate that the family 22 carbohydrate binding module is
not a potential candidate for use in in planta modification of the cell wall
HIGH FREQUENCY MULTIPLE SHOOTS INDUCTION AND PLANT REGENERATION IN SIX ELITE INDIAN COTTON CULTIVARS
Direct multiple shoot induction and regeneration from the cotyledonary nodal explants of two Indian cultivars of upland
cotton, G. hirsutum (hybrid H8 and Khandwa-2) and four cultivars of G. arboretum (BD-1, BD-6, Sarvottam and
Jawahar Tapti BD) were investigated, using varying concentrations of BAP. An overall average of 5.5 shoots per explant
was achieved in the study. The best multiple shoots formation (9 shoots per explant) was obtained from the two G.
hirsutum cultivars cultured on 3.0 mg L-1 BAP. Shoots were harvested and elongated in the presence of 0.5 mg L-1 GA3.
Root formation was achieved on hormone-free MS medium
STUDIES ON KOLA TISSUE CULTURE I: Protocols for Establishing Kola Tissues in vitro
The micropropagation of Cola nitida (Vent.) Schott and Endlicher by means of tissue culture was
investigated to provide baseline infonnation on the requ irements for the survival of kola tissues and
organs in vitro. Investigations were conducted on development of sterilization protocols, and medium
selection and modification. The best sterilization procedure was established with the step-wise
treatment of 70% ethanol, for 20 seconds and 10% (w/v) CaOCl, for I 0 minutes .. The use of modified
Murashige-Skoog (MS) medium (without Zn and Cu elements) as basal medium was found as
appropriate as the original MS medium, for explants' survival. The appropriate antioxidant technique
was also established with 10mgl-1 ascorbic acid
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