Richard J. Henny

AFLP analysis of nephthytis (Syngonium podophyllum Schott) selected from somaclonal variants.

This study analyzed genetic differences of 19 cultivars selected from somaclonal variants of Syngonium podophyllum Schott along with their parents as well as seven additional Syngonium species and six other aroids using amplified fragment length polymorphism (AFLP) markers generated by 12 primer sets. Among the 19 somaclonal cultivars, ‘Pink Allusion’ was selected from ‘White Butterfly’. Tissue culture of ‘Pink Allusion’ through organogenesis resulted in the development of 13 additional cultivars. Self-pollination of ‘Pink Allusion’ obtained a cultivar, ‘Regina Red Allusion’, and tissue culture propagation of ‘Regina Red Allusion’ led to the release of five other cultivars. The 12 primer sets generated a total of 1,583 scorable fragments from all accessions, of which 1,284 were polymorphic (81.9%). The percentages of polymorphic fragments within ‘White Butterfly’ and ‘Regina Red Allusion’ groups, however, were only 1.2% and 0.4%, respectively. Jaccards similarity coefficients among somaclonal cultivars derived from ‘White Butterfly’ and ‘Regina Red Allusion’, on average, were 0.98 and 0.99, respectively. Seven out of the 15 cultivars from the ‘White Butterfly’ group and three out of six from the ‘Regina Red Allusion’ group were clearly distinguished by AFLP analysis as unique fragments were associated with respective cultivars. The unsuccessful attempt to distinguish the remaining eight cultivars from the ‘White Butterfly’ group and three from the ‘Regina Red Allusion’ group was not attributed to experimental errors or the number of primer sets used; rather it is hypothesized to be caused by DNA methylation and/or some rare mutations. This study also calls for increased genetic diversity of cultivated Syngonium as they are largely derived from somaclonal variants.

Gibberellic acid affects growth and flowering of Philodendron 'Black Cardinal'

A single foliar spray of gibberellic acid (GA3) at concentrations of 125, 250, 500, or 1,000 mg L−1 induced flowering of Philodendron‘Black Cardinal’ (an interspecific hybrid developed from a series of crosses among P. wendlandii, hastatum, erubescens, imbe, fragrantissimum, and an unnamed species) in approximately 170 d. Percentage of plants induced and mean flower number per plant increased as GA3 concentrations increased. Compared to unsprayed plants, the number of new leaves decreased, petiole lengths of new leaves and length of the largest leaf increased, but leaf width was unaffected among sprayed plants. One hour before the spathe started to unfurl, spadix temperatures increased, and temperatures in the male portion of the spadix rose by 10 °C above ambient as the spathe fully opened. Elevated temperatures were recorded for about two hours and returned to ambient within five hours. Spathes remained open for about five hours. A creamy white spadix with a contrasting burgundy spathe resulted in more aesthetically pleasing plants than with foliage alone. Because of the short period of display, the open spathe would not increase additional ornamental value of Philodendron‘Black Cardinal’ in the marketplace. However, if breeding is the purpose of flowering induction, spathes should be cut away from the spadix to facilitate pollination.

Thidiazuron promotes adventitious shoot regeneration from pothos (Epipremnum aureum) leaf and petiole explants

SummaryRegeneration of adventitious shoots of pothos (Epipremnum aureum Linden and Andre) ‘Jade’ was obtained using leaf and petiole explants preprated from shoot tips of 3-yr-old greenhouse-grown plants. Explants were cultured on Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ), 6-(4-hydroxy-3-methy-trans-2-butenyl-amino)purine (zeatin) or N-isopentenylaminopurine (2iP) individually with α-naphthaleneacetic acid (NAA) in 18 combinations. Callus was initiated from cut surface and along the midrib or major vein of leaf sections. Shoot regeneration from leaf and petoole explants occurred in 30d on medium containing 1, 5 or 10μM TDZ with 0.5 or 1.0μM NAA except petioles on medium with 10 μM TDZ and 1.0 μM NAA where regeneration failed. More time (50d) was needed for shoot regeneration when explants were cultured on medium containing either 2iP or zeatin with NAA. Regeneration frequencies were up to 20% and 50% for leaf and petiole explants, respectively. Shoot numbers per responding explant attained 30 for leaf and petiole explants on medium containing TDZ but only one to four on medium containing either 2iP or zeatin. These results indicate that TDZ is a more effective cytokinin for in vitro regeneration of pothos than either zeatin or 2iP.. Shoots elongated readily and rooted well on MS basal medium, without plant growth regulators. Plantlets acclimatized rapidly and grew vigorously in the greenhouse after transfer to pots containing a commerecial potting medium.

Gibberellin deficiency is responsible for shy-flowering nature of Epipremnum aureum.

Epipremnum aureum is an extremely popular houseplant belonging to the Araceae family of angiosperms, but it does not flower either in the wild or under cultivation. We uncovered the potential causes of its shy-flowering nature by building the transcriptome using next-generation sequencing and identifying floral-related genes that are differentially expressed between vertical growth (VG, adult) and horizontal growth (HG, juvenile) plants. Transcripts of the gibberellin (GA) biosynthetic gene EaGA3ox1 and GA-responsive floral meristem identity gene EaLFY were absent in both VG and HG plants, suggesting that a deficiency of bioactive GAs may be responsible for its shy-flowering nature. This hypothesis is supported by undetectable or low levels of three bioactive GAs, and exogenous GA3 triggered flowering in both plants. Our study resolves the mystery why E. aureum fails to flower, and reveals the positive role of GAs in floral transition in perennials.

Interspecific relationships of Alocasia revealed by AFLP analysis

Summary This study analysed genetic relationships of 23 Alocasia cultivars across 17 species using amplified fragment length polymorphism (AFLP) markers. Six primer sets, selected from an initial screening of 48, generated a total of 578 scorable AFLP fragments of which 334 (58.4%) were polymorphic. All cultivars were clearly detected by their AFLP fingerprints. A dendrogram was constructed using the unweighted pair-group method of arithmetic averages (UPGMA). Principal coordinated analysis (PCOA) was carried out to show multiple dimensional distributions of cultivars. Both UPGMA and PCOA analyses separated the 23 cultivars into three clusters. Cluster I comprises 16 cultivars, mainly derived from A. crassifolia, A. cuprea, A. longiloba, A. grandis, A. guttata, A. plumbea, A. macrorrhiza, A. micholitziana, and A. villeneuvei or hybrids of A. lowii A. sanderiana and A. cuprea A. veitchii. Jaccard’s similarity coefficients for these species ranged from 0.43 to 0.77. Cluster II contains six cultivars, which include A. cadieri, A. cucullata, A. gageana, A. odora, and A. portei. Jaccard’s similarity coefficients varied from 0.52 to 0.83. There is only one cultivar, ‘Hilo Beauty’ in the cluster III, whose low similarity (0.21) with the rest of the Alocasia species may suggest that it could actually belong to another genus of Araceae. Based on documented interspecific hybrids, it appears that hybrids were developed from species exclusively within the identified clusters. This may suggest that Alocasia species sharing high Jaccard’s similarity coefficients are more likely to be intercrossable. The interspecific relationships detected by the AFLP analysis could provide the genetic basis for selecting parents for future hybrid development.

Accumulation of high OPDA level correlates with reduced ROS and elevated GSH benefiting white cell survival in variegated leaves

Variegated ‘Marble Queen’ (Epipremnum aureum) plant has white (VMW) and green (VMG) sectors within the same leaf. The white sector cells containing undifferentiated chloroplasts are viable, but the underlying mechanism for their survival and whether these white cells would use any metabolites as signal molecules to communicate with the nucleus for maintaining their viability remain unclear. We analyzed and compared phytohormone levels with their precursors produced in chloroplasts between VMW and VMG, and further compared their transcriptomes to understand the consequences related to the observed elevated 12-oxo phytodienoic acid (OPDA), which was 9-fold higher in VMW than VMG. Transcriptomic study showed that a large group of OPDA-responsive genes (ORGs) were differentially expressed in VMW, including stress-related transcription factors and genes for reactive oxygen species (ROS) scavengers, DNA replication and repair, and protein chaperones. Induced expression of these ORGs could be verified in OPDA-treated green plants. Reduced level of ROS and higher levels of glutathione in VMW were further confirmed. Our results suggest that elevated OPDA or its related compounds are recruited by white cells as a signaling molecule(s) to up-regulate stress and scavenging activity related genes that leads to reduced ROS levels and provides survival advantages to the white cells.

Differential expression of a novel gene EaF82a in green and yellow sectors of variegated Epipremnum aureum leaves is related to uneven distribution of auxin

EaF82, a gene identified in previous studies of the variegated plant Epipremnum aureum, exhibited a unique expression pattern with greater transcript abundance in yellow sectors than green sectors of variegated leaves, but lower abundance in regenerated pale yellow plants than in green plants derived from leaf tissue culture. Studies of its full-length cDNA and promoter region revealed two members with only the EaF82a expressed. Immunoblotting confirmed that EaF82a encodes a 12 kDa protein and its accumulation consistent with its gene expression patterns in different color tissues. Transient expression of EaF82a-sGFP fusion proteins in protoplasts showed that EaF82a seems to be present in the cytosol as unidentified spots. Sequence motif search reveals a potential auxin responsive element in promoter region. Using transgenic Arabidopsis seedlings carrying EaF82a promoter driving the bacterial uidA (GUS) gene, an increased GUS activity was observed when IAA (indole-3-acetic acid) concentration was elevated. In E. aureum, EaF82a is more abundant at the site where axillary buds emerge and at the lower side of bending nodes where more IAA accumulates relative to the upper side. The measurement of endogenous IAA levels in different color tissues revealed the same pattern of IAA distribution as that of EaF82a expression, further supporting that EaF82a is an IAA responsive gene. EaF82a expression in etiolated transgenic Arabidopsis seedlings responded to IAA under the influence of light suggesting a microenvironment of uneven light condition affects the EaF82a transcript levels and protein accumulation in variegated leaves.