Involvement of alpha-amylase I-1 in starch degradation in rice chloroplasts

To determine the role of alpha-amylase isoform I-1 in the degradation of starch in rice leaf chloroplasts, we generated a series of transgenic rice plants with suppressed expression or overexpression of alpha-amylase I-1. In the lines with suppressed expression of alpha-amylase I-1 at both the mRNA and protein levels, seed germination and seedling growth were markedly delayed in comparison with those in the wild-type plants. However, the growth retardation was overcome by supplementation of sugars. Interestingly, a significant increase of starch accumulation in the young leaf tissues was observed under a sugar-supplemented condition. In contrast, the starch content of leaves was reduced in the plants overexpressing alpha-amylase I-1. In immunocytochemical analysis with specific anti-alpha-amylase I-1 antiserum, immuno-gold particles deposited in the chloroplasts and extracellular space in young leaf cells. We further examined the expression and targeting of alpha-amylase I-1 fused with the green fluorescent protein in re-differentiated green cells, and showed that the fluorescence of the expressed fusion protein co-localized with the chlorophyll autofluorescence in the transgenic cells. In addition, mature protein species of alpha-amylase I-1 bearing an oligosaccharide side chain were detected in the isolated chloroplasts. Based on these results, we concluded that alpha-amylase I-1 targets the chloroplasts through the endoplasmic reticulum-Golgi system and plays a significant role in the starch degradation in rice leaves.     

Influence of meristem-tip size and location on morphological development in Dioscorea cayenensis-D. rotundata complex ‘Grosse Caille’ and one genotype of D. praehensilis

In vitro morphological development of meristem-tips, excised from microshoots, is reported for one clone Grosse Caille of D. cayenensis-D. rotundata complex and for one clone of D. praehensilis. The effects of size and location of meristem-tip on viability and morphological development after 3, 8 and 11 months in vitro culture were studied. The larger size of meristem-tip gave the best rooting and plantlet formation while the smaller size gave the best bud production. Axillary buds were more reactive than apical meristem-tips in callusing and rooting when small-sized meristems of the Grosse Caille clone were used; the use of larger meristem-tips did not induce more differences between apical and axillary buds. The production of plantlets was successful, after 11 months of culture, with a score of 82 and 39 % survivors, for Grosse Caille clone and D. praehensilis genotype, respectively.Abbreviations Ap apical meristem-tips - ApLS large-sized apical meristem-tips - Ax axillary meristem-tips - AxLS large-sized axillary meristem-tips - BA 6-benzyladenine - cv cultivar - LS large-sized meristem-tip - NAA naphthalenacetic acid - SS small-sized meristem-tip     

Effect of growth regulators concentrations on morphological development of meristem-tips in Dioscorea cayenensis-D. rotundata complex and D. praehensilis

The use of the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-d) has played an important role in the production and maintenance of totipotent cereal callus. However, 2,4-d has been implicated in the loss of totipotency from barley callus. To examine the effect of 2,4-d on barley callus, regenerability and karyotype were examined over time as influenced by cultivar differences and 2,4-d levels, during a period in which initially vigorous plant regeneration typically declines dramatically. Higher (20.4–27.1 M) versus lower (6.8–13.6 M) concentrations of 2,4-d were positively associated with the number of green plantlets recovered from calli maintained for 10 and 16 weeks before transfer to regeneration media, and with the longevity of regenerability. There was a positive relationship between 2,4-d concentration and normal karyotype. We also investigated the use of phenylacetic acid for the initiation of regenerable barley callus. Very poor callus growth and plant regeneration was supported by phenylacetic acid.Abbreviations PAA phenylacetic acid - SPDL(s) single plant-derived lines(s) - 2,4-d 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog (1962) - MSO Murashige and Skoog medium lacking growth regulators     

Generalizable brain network markers of major depressive disorder across multiple imaging sites

Many studies have highlighted the difficulty inherent to the clinical application of fundamental neuroscience knowledge based on machine learning techniques. It is difficult to generalize machine learning brain markers to the data acquired from independent imaging sites, mainly due to large site differences in functional magnetic resonance imaging. We address the difficulty of finding a generalizable marker of major depressive disorder (MDD) that would distinguish patients from healthy controls based on resting-state functional connectivity patterns. For the discovery dataset with 713 participants from 4 imaging sites, we removed site differences using our recently developed harmonization method and developed a machine learning MDD classifier. The classifier achieved an approximately 70% generalization accuracy for an independent validation dataset with 521 participants from 5 different imaging sites. The successful generalization to a perfectly independent dataset acquired from multiple imaging sites is novel and ensures scientific reproducibility and clinical applicability.

Biomarkers for psychiatric disorders based on neuroimaging data have yet to be put to practical use. This study overcomes the problems of inter-site differences in fMRI data by using a novel harmonization method, thereby successfully constructing a generalizable brain network marker of major depressive disorder across multiple imaging sites.