Improving of rooting and ex vitro acclimatization phase of Agave tequilana by temporary immersion system (BioMINT™)

In Vitro Cellular & Developmental Biology - Plant -     

Cyclic AMP regulates the biosynthesis of cellobiohydrolase in <Emphasis Type="Italic">Cellulomonas flavigena</Emphasis> growing in sugar cane bagasse

Cellulomonas flavigena produces a battery of cellulase components that act concertedly to degrade cellulose. The addition of cAMP to repressed C. flavigena cultures released catabolic repression, while addition of cAMP to induced C. flavigena cultures led to a cellobiohydrolase hyperproduction. Exogenous cAMP showed positive regulation on cellobiohydrolase production in C. flavigena grown on sugar cane bagasse. A C. flavigena cellobiohydrolase gene was cloned (named celA), which coded for a 71- kDa enzyme. Upstream, a repressor celR1, identified as a 38 kDa protein, was monitored by use of polyclonal antibodies.     

Influence of form of activated charcoal on embryogenic callus formation in coconut (<Emphasis Type="Italic">Cocos nucifera</Emphasis>)

Development of micropropagation protocols for Cocos nucifera has progressed slowly. Activated charcoal is included in the culture medium of each protocol, mainly to prevent tissue browning. Charcoal production procedures can affect the properties of different brands. In this study, eight types of activated charcoal were evaluated for their effects on free 2,4-dichlorophenoxyacetic acid level, pH, conductivity, and osmolarity of the culture medium and on the frequency of embryogenic callus induction. Moreover, the effect of particle size of the optimum charcoal type on embryogenic callus development was also studied. Charcoal type had a significant effect on (Y3) culture medium properties. Free 2,4-D was highest in Reactivos y Productos Químicos Finos-containing medium and pH was lowest in MERCK-containing medium. Charcoal type also influenced embryogenic callus induction, with acid washed for plant cell and tissue culture-, DARCO- and United States Pharmacopeia-containing media promoting ~60% embryogenic callus, but with different optimal 2,4-D concentrations. Particle size profiles varied among all charcoal types, although small particle fraction (<38 μm) was abundant in all. Use of small particle fractions produced higher frequencies of embryogenic callus (70%) than either large particle or whole charcoal fractions.     

Reproductive biology of henequen (Agave fourcroydes) and its wild ancestor Agave Angustifolia (Agavaceae). i. Gametophyte development

The pathways of micro- and megagametophyte development in Agave fourcroydes (henequén) and A. angustifolia were studied. We used histology and light microscopy to observe anther ontogeny and ovary differentiation in relation to flower bud size. Both species have the same sexual reproductive strategies and gametophyte development that may be divided into three phases: (1) premeiotic, which includes the establishment of the megaspore mother cell and the pollen mother cell; (2) meiotic, the formation of mature microspores and functional megaspores; (3) postmeiotic, which encompasses the development of mature pollen grains and the formation of the embryo sac. A successive type microsporogenesis was found in both species with formation of T-shaped tetrads and binuclear pollen grains. In vitro germination tests revealed very low pollen fertility. The female gametophyte is formed from two micropylar megaspore cells after the first meiotic division (bisporic type). Male and female gametogenesis occur asynchronously with microsporogenesis finishing before macrosporogenesis. The results so far show that the formation of male and female gametophytes in henequén is affected at different stages and that these alterations might be responsible for the low fertility shown by this species.