Ethylene and light act through specific signal transduction mechanisms to coordinate the development of higher plants. Application of 1-aminocyclopropane-1-carboxylic acid (ACC, an ethylene precursor) suppresses the hypocotyl elongation of Arabidopsis seedlings in dark, but stimulates it in light. However, the mechanisms of opposite effects of ethylene on hypocotyl elongation in light and dark remain unclear. In the present study, we investigated the key factors involved in the opposite effects of ethylene on hypocotyl elongation in Arabidopsis seedlings. The effects of ACC on hypocotyl elongation of IAA-insensitive mutants including tir1-1, axr1-3, and axr1-12 seedlings were reduced in light but not in dark. The DR5 promoter, a synthetic auxin-response promoter, was used to quantify the level of IAA responses. There was a marked increase in DR5-GFP signals in response to ACC treatment in hypocotyls of DR5-GFP seedlings in light, but not in dark. CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) is an important downstream component of light signaling. ETHYLENE-INSENSITIVE3 (EIN3, an ethylene-stabilized transcription factor) directly regulates ETHYLENE-RESPONSE-FACTOR1 (ERF1). The cop1-4 mutant treated with ACC and cop1-4/EIN3ox plants developed long hypocotyls in darkness. Expression of ERF1 in the cop1-4 mutant was induced by ACC treatment in dark, but the expression of ERF1 in the wild type was not affected. Taken together, ethylene-promoting hypocotyl via IAA is mediated by light, and COP1 has a significant impact on the transcription of some genes downstream of EIN3. Thus, COP1 plays a crucial role in the opposite effects of ethylene on hypocotyl elongation.

The APETALA1 (AP1)/FRUITFULL (FUL)-like transcription factor OsMADS18 plays diverse functions in rice development, but the underlying molecular mechanisms are far from fully understood. Here, we report that down-regulation of OsMADS18 expression in RNAi lines caused a delay in seed germination and young seedling growth, whereas the overexpression of OsMADS18 produced plants with fewer tillers. In targeted OsMADS18 genome-edited mutants (osmads18-cas9), an increased number of tillers, altered panicle size, and reduced seed setting were observed. The EYFP-OsMADS18 (full-length) protein was localized to the nucleus and plasma membrane but the EYFP-OsMADS18-N (N-terminus) protein mainly localized to the nucleus. The expression of OsMADS18 could be stimulated by abscisic acid (ABA), and ABA stimulation triggered the cleavage of HA-OsMADS18 and the translocation of OsMADS18 from the plasma membrane to the nucleus. The inhibitory effect of ABA on seedling growth was less effective in the OsMADS18-overexpressing plants. The expression of a set of ABA-responsive genes was significantly reduced in the overexpressing plants. The phenotypes of transgenic plants expressing EYFP-OsMADS18-N resembled those observed in the osmads18-cas9 mutants. Analysis of the interaction of OsMADS18 with OsMADS14, OsMADS15, and OsMADS57 strongly suggests an essential role for OsMADS18 in rice development.

The sturgeon (Acipenseriformes) is an important farmed species because of its economical value. However, neither gene transfer nor gene editing techniques have been established in sturgeon for molecular breeding and gene functional study until now. In this study, we accomplished gene transfer and gene editing in sterlet (Acipenser ruthenus), which has the shortest sexual maturation period of sturgeons. The plasmid encoding enhanced green fluorescent protein (EGFP) was transferred into the embryos of sterlet at injection concentration of 100 ng/μL, under which condition high survival rate and gene transfer rate could be achieved. Subsequently, exogenous EGFP was efficiently disrupted by transcription activator-like effector nucleases (TALENs) or clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 nuclease/guide RNA (gRNA), with injection concentrations of 300 ng/μL TALENs, or 100 ng/μL Cas9 nuclease and 30 ng/μL gRNA, respectively, under which condition high survival rate and gene mutation rate could be achieved. Finally, the endogenous gene no tail in sterlet was successfully mutated by Cas9 nuclease/gRNA. We observed the CRISPR-induced no tail mutation, at a high efficiency with the mutant P0 embryos displaying the expected phenotype of bent spine and twisted tail.

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