Transient expression of a green fluorescent protein in tobacco and maize chloroplast

BACKGROUND: Maize is one of the most important crops worldwide and has been a target of nuclear-based transformation biotechnology to improve it and satisfy the food demand of the ever-growing global population. However, the maize plastid transformation has not been accomplished due to the recalcitrant condition of the crop. RESULTS: In this study, we constructed two different vectors with homologous recombination sequences from maize (Zea mays var. LPC13) and grass (Bouteloua gracilis var. ex Steud) (pZmcpGFP and pBgcpGFP, respectively). Both vectors were designed to integrate into rrn23S/rrn16S from an inverted repeat region in the chloroplast genome. Moreover, the vector had the mgfp5 gene driven by Prrn, a leader sequence of the atpB gene and a terminator sequence from the rbcL gene. Also, constructs have an hph gene as a selection marker gene driven by Prrn, a leader sequence from rbcL gene and a terminator sequence from the rbcL gene. Explants of maize, tobacco and Escherichia coli cells were transformed with both vectors to evaluate the transitory expression­an exhibition of green and red fluorescent light under epifluorescence microscopy. These results showed that both vectors were expressed; the reporter gene in all three organisms confirmed the capacity of the vectors to express genes in the cell compartments. CONCLUSIONS: This paper is the first report of transient expression of GFP in maize embryos and offers new information for genetically improving recalcitrant crops; it also opens new possibilities for the improvement in maize chloroplast transformation with these vectors.

Diurnal regulation of plastid genes in Populus deltoides.

Light regulates leaf and chloroplast development, together with overall chloroplast gene expression at various levels. Plants respond to diurnal and seasonal changes in light by changing expression of photosynthesis genes and metabolism. In Populus deltoides, a deciduous tree species, leaf development begins in the month of March and leaf maturation is attained by summer, which is subsequently followed by autumnal senescence and fall. In the present study, diurnal changes in the steady state transcript levels of plastid genes were examined in the fully developed leaves during summer season. Our results show that steady state level of the psaA/B, psbA, psbEFLJ and petA transcripts showed differential accumulation during diurnal cycle in summer. However, there was no significant change in the pigment composition during the day/night cycle. Our studies suggest that the diurnal regulation of steady state mRNA accumulation may play a crucial role during daily adjustments in plants life with rapidly changing light irradiance and temperature.