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In papaya, the low rooting capacity of in vitro cultivated plants increases their mortality rates during ex vitro acclimatization, further limiting the exploitation of this plant regeneration system, especially for the elite cultivar 'Maradol Roja'. Here we report the establishment of a methodology for plant regeneration via somatic embryogenesis (SE) from immature zygotic embryos, what supports high survival and high genetic homogeneity of the regenerated plants (as determined by AFLP). It was demonstrated the expression of AUX/LAX and PIN genes coding for auxin polar transporters at different stages of SE, a novel aspect for this crop. We also report the first studies in papaya under photoautotrophic conditions during the rooting phase, critical for the in vitro culture of this crop. The use of growth regulators Pectimorf® and phloroglucinol, zeolite as support, and culture flasks with increased ventilation for rooting and in vitro acclimatization, derived in positive effects on ex vitro acclimatization. The incorporation of the RITA® temporary immersion system to the methodology guarantees the high efficiency of the SE system. These are novel and promising findings which make more efficient the in vitro regeneration system. The results are also unprecedented in papaya, particularly for the 'Maradol Roja' cultivar of high commercial value. This work granted the Annual Award of the National Academy of Sciences of Cuba for the year 2016. [ABSTRACT FROM AUTHOR]

Micropropagation is an important tool for the multiplication of native Cerrado species. However, understanding the responses of these species under in vitro culture conditions is still incomplete. Thus, the present study aimed to analyze the growth, anatomical behavior and physiology of Pouteria gardneriana cultivated in vitro under photoautotrophic conditions. Nodal segments were cultured at photosynthetic photon flux densities (PPFD) of 75, 100 and 150 μmol m-2 s-1 in culture medium MS 50% solidified with 3.5 g L-1 of agar and 2.0 g L-1 of activated charcoal, in the absence and presence of 30 g L-1 of sucrose. After 60 days of in vitro culture, the P. gardneriana plantlets only regenerated when sucrose was present in the culture medium. Higher fresh and dry weights, higher palisade parenchyma thickness and larger stomatal polar and equatorial diameters were observed in the plantlets cultured at PPFD 150 μmol m-2 s-1. The PPFD difference used in the present study was sufficient to provide additional understanding of the behavior of this species in vitro. [ABSTRACT FROM AUTHOR]

This communication describes the construction and operation of an airlift fermenter for the photoautotrophic growth of cell suspension cultures from Chenopodium rubrum. The basic batch culture unit provides a culture of 1.51 volume, sufficient to permit frequent aseptic sampling. It can be maintained at any desired temperature and aerated to different extents. Using an initial cell density of about 400,000 cells per ml suspension, the increase in cell number is 270% after a 14 days' growth period, although the stationary phase of growth is not yet reached. The transfer of photoautotrophic cell suspensions from Chenopodium rubrum from stationary growth into the large volume of fresh culture medium in the airlift fermenter results in an immediate protein formation, followed by an exponential phase of cell division, whereas rapid chlorophyll accumulation is delayed by 2 days. The growth capacities of photoautotrophic fermenter cultures including protein and chlorophyll formation as well as in vitro activities of the ribulosebisphosphate carboxylase and the phosphoenolpyruvate carboxylase are greatly lower as compared to photoautotrophic cells propagated in standard two-tier culture vessels using 30 ml culture medium. However the pattern of change in the activities of carboxylation enzymes is quite similar in both culture systems. Photoautotrophic cell suspensions from Chenopodium rubrum grown in an airlift fermenter assimilate about 90 μmol CO/mg chlorophyll × hour. Dark CO fixation is about 1.5% of the light values. [ABSTRACT FROM AUTHOR]

This communication reports the photoautotrophic growth of hormone and vitamin independent cell suspension cultures of Chenopodium rubrum. The transfer of cells from stationary growth into fresh culture medium results in a high protein formation, followed by an exponential phase of cell division, whereas the onset of rapid chlorophyll formation is delayed for 4 days. At the stage of most rapid cell division there is no net synthesis of starch and sugar. When the cells enter stationary growth, there is a progressive accumulation of chlorophyll, sugar, and starch. Photoautotrophic cell cultures assimilate about 80-90 μmol CO/mg chlorophyll X hour. Dark CO fixation is about 3.7% to 2.2% of the light values during exponential and stationary growth, respectively. As shown by short-termCO fixation, CO is predominantly assimilated through ribulosebisphosphate carboxylase via the Calvin pathway. There is a significant increase in theC label of C carboxylic acids in exponentially dividing cells as compared to cells from stationary growth. The in vitro activity of phosphoenolpyruvate carboxylase and ribulosebisphosphate carboxylase is almost equal during exponential cell division. A decrease in cell division activity is accompanied by a significant change in the specific activities of both carboxylation enzymes. In non dividing cells from stationary growth the activity of ribulosebisphosphate carboxylase is greately enhanced and that of phosphoenolpyruvate carboxylase is reduced, documenting the development of carboxylation capacities typical for C-plants. The experimental results provide evidence that phosphoenolpyruvate carboxylase activity might be regulated by ammonia and could be involved in anaplerotic CO fixation which supplies carbon skeletons of the citric acid cycle. [ABSTRACT FROM AUTHOR]

Cell suspension cultures of Chenopodium rubrum have been grown for more than 2 years photoautotrophically with CO as sole carbon source. Average increase in fresh weight is appr. 600% within 14 days. The chlorophyll content of photoautotrophic cells (200 μg/g fresh weight) is much higher than of photomixotrophic cells (50 μg/g fresh weight). The photosynthetic activity of the cells (190 μmoles CO×mg chlorophyllXh) is comparable to the values found with intact leaves. As shown by short-termCO photosynthesis, both, the photomixotrophic and the photoautotrophic cell suspension cultures assimilate CO predominantly via the Calvin pathway. Major differences were found with cells from either exponential or stationary phase of growth with regard to differential labelling of 3-phosphoglyceric acid, malate, sucrose and glucose/fructose. In vitro measurements of carboxylation reactions only partially corroborate our findings withCO incorporation. The ratio of ribulosebisphosphate to phosphoenolpyruvate carboxylase activity is 4.7 for leaves of C. rubrum, 1.2 for photoautotrophic cells during stationary growth and 0.5 for cells during exponential growth phase, however, 0.18 was found for photomixotrophic cells. Though theCO incorporation into 3-phosphoglyceric acid is clearly higher than into malate, the in vitro activity of phosphoenolpyruvatecarboxylase is 2-6 fold higher than that of ribulosebisphosphate carboxylase. We postulate that anaplerotic reactions of the tricarboxylic acid cycle are involved in the regulation of phosphoenolpyruvate carboxylase. [ABSTRACT FROM AUTHOR]