Cell expansion is crucial for plant growth. It is well known that the phytohormone ethylene functions in plant development as a key modulator of cell expansion. However, the role of ethylene in the regulation of this process remains unclear. In this study, 2,189 ethylene-responsive transcripts were identified in rose (Rosa hybrida) petals using transcriptome sequencing and microarray analysis. Among these transcripts, an NAC (for no apical meristem [NAM], Arabidopsis transcription activation factor [ATAF], and cup-shaped cotyledon [CUC])-domain transcription factor gene, RhNAC100, was rapidly and dramatically induced by ethylene in the petals. Interestingly, accumulation of the RhNAC100 transcript was modulated by ethylene via microRNA164-dependent posttranscriptional regulation. Overexpression of RhNAC100 in Arabidopsis (Arabidopsis thaliana) substantially reduced the petal size by repressing petal cell expansion. By contrast, silencing of RhNAC100 in rose petals using virus-induced gene silencing significantly increased petal size and promoted cell expansion in the petal abaxial subepidermis (P , 0.05). Expression analysis showed that 22 out of the 29 cell expansion-related genes tested exhibited changes in expression in RhNAC100-silenced rose petals. Moreover, of those genes, one cellulose synthase and two aquaporin genes (Rosa hybrida Cellulose Synthase2 and R. hybrida Plasma Membrane Intrinsic Protein1;1/2;1) were identified as targets of RhNAC100. Our results suggest that ethylene regulates cell expansion by fine-tuning the microRNA164/RhNAC100 module and also provide new insights into the function of NAC transcription factors.

We developed an easy-traceable TRV vector, TRV2-GFP, by tagging a GFP to the coat protein. TRV2-GFP-infected plants could be identified efficiently by GFP monitoring. TRV2-GFP is useful for functional genomics in many plants, especially for non-Solanaceae plants, like rose

No abstract

MicroRNAs play an important role in plant development and plant responses to various biotic and abiotic stimuli. As one of the most important ornamental crops, rose (Rosa hybrida) possesses several specific morphological and physiological features, including recurrent flowering, highly divergent flower shapes, colors and volatiles. Ethylene plays an important role in regulating petal cell expansion during rose flower opening. Here, we report the population and expression profiles of miRNAs in rose petals during flower opening and in response to ethylene based on high throughput sequencing. We identified a total of 33 conserved miRNAs, as well as 47 putative novel miRNAs were identified from rose petals. The conserved and novel targets to those miRNAs were predicted using the rose floral transcriptome database. Expression profiling revealed that expression of 28 known (84.8% of known miRNAs) and 39 novel (83.0% of novel miRNAs) miRNAs was substantially changed in rose petals during the earlier opening period. We also found that 28 known and 22 novel miRNAs showed expression changes in response to ethylene treatment. Furthermore, we performed integrative analysis of expression profiles of miRNAs and their targets. We found that ethylene-caused expression changes of five miRNAs (miR156, miR164, miR166, miR5139 and rhy-miRC1) were inversely correlated to those of their seven target genes. These results indicate that these miRNA/target modules might be regulated by ethylene and were involved in ethylene-regulated petal growth.

Ethylene plays an important role in organ growth. In Arabidopsis, ethylene can inhibit root elongation by stabilizing DELLA proteins. In previous work, it was found that ethylene suppressed cell expansion in rose petals, and five unisequences of DELLA genes are induced by ethylene. However, the mechanism of transcriptional regulation of DELLA genes by ethylene is still not clear. The results showed that the expression of RhGAI1 was induced in both ethylene-treated and ETR gene-silenced rose petals, and the promoter activity of RhGAI1 was strongly induced by RhEIN3-3 in Arabidopsis protoplasts. What is more, RhEIN3-3 could bind to the promoter of RhGAI1 directly in an electrophoretic mobility shift assay (EMSA). Cell expansion was suppressed in RhGAI1-Δ17-overexpressed Arabidopsis petals and promoted in RhGAI1-silenced rose petals. Moreover, in RhGAI1-silenced petals, the expression of nine cell expansion-related genes was clearly changed, and RhGAI1 can bind to the promoter of RhCesA2 in an EMSA. These results suggested that RhGAI1 was regulated by ethylene at the transcriptional level, and RhGAI1 was a direct target of RhEIN3-3. Also, RhGAI1 was shown to be involved in cell expansion partially through regulating the expression of cell expansion-related genes. Furthermore, RhCesA2 was a direct target of RhGAI1. This work uncovers the transcriptional regulation of RhGAI1 by ethylene and provides a better understanding of how ethylene regulates petal expansion in roses.

The plant hormone ethylene plays various functions in plant growth, development and response to environmental stress. Ethylene is perceived by membrane-bound ethylene receptors, and among the homologous receptors in Arabidopsis, the ETR1 ethylene receptor plays a major role. The present study provides evidence demonstrating that Arabidopsis CPR5 functions as a novel ETR1 receptor-interacting protein in regulating ethylene response and signaling. Yeast split ubiquitin assays and bi-fluorescence complementation studies in plant cells indicated that CPR5 directly interacts with the ETR1 receptor. Genetic analyses indicated that mutant alleles of cpr5 can suppress ethylene insensitivity in both etr1-1 and etr1-2, but not in other dominant ethylene receptor mutants. Overexpression of Arabidopsis CPR5 either in transgenic Arabidopsis plants, or ectopically in tobacco, significantly enhanced ethylene sensitivity. These findings indicate that CPR5 plays a critical role in regulating ethylene signaling. CPR5 is localized to endomembrane structures and the nucleus, and is involved in various regulatory pathways, including pathogenesis, leaf senescence, and spontaneous cell death. This study provides evidence for a novel regulatory function played by CPR5 in the ethylene receptor signaling pathway in Arabidopsis.

Ethylene as a gaseous plant hormone is directly involved in various processes during plant growth and development. Much is known regarding the ethylene receptors and regulatory factors in the ethylene signal transduction pathway. In Arabidopsis thaliana, REVERSION-TO-ETHYLENE SENSITIVITY1 (RTE1) can interact with and positively regulates the ethylene receptor ETHYLENE RESPONSE1 (ETR1). In this study we report the identification and characterization of an RTE1-interacting protein, a putative Arabidopsis lipid transfer protein 1 (LTP1) of unknown function. Through bimolecular fluorescence complementation, a direct molecular interaction between LTP1 and RTE1 was verified in planta. Analysis of an LTP1-GFP fusion in transgenic plants and plasmolysis experiments revealed that LTP1 is localized to the cytoplasm. Analysis of ethylene responses showed that the ltp1 knockout is hypersensitive to 1-aminocyclopropanecarboxylic acid (ACC), while LTP1 overexpression confers insensitivity. Analysis of double mutants etr1-2 ltp1 and rte1-3 ltp1 demonstrates a regulatory function of LTP1 in ethylene receptor signaling through the molecular association with RTE1. This study uncovers a novel function of Arabidopsis LTP1 in the regulation of ethylene response and signaling.

No abstract