No abstract

In non-climacteric fruits, the respiratory increase is absent and no phytohormone is appearing to be critical for their ripening process. They must remain on the parent plant to enable full ripening and be picked at or near the fully ripe stage to obtain the best eating quality. However, huge losses often occur for their quick post-harvest senescence. To understanding the complex mechanism of non-climacteric fruits post-harvest senescence, we constructed two small RNA libraries and one degradome from strawberry fruit stored at 20°C for 0 and 24 h. A total of 88 known and 1224 new candidatemiRNAs, and 103 targets cleaved by 19 known miRNAs families and 55 new candidatemiRNAs were obtained. These targets were associated with development, metabolism, defense response, signaling transduction and transcriptional regulation. Among them, 14 targets, including NAC transcription factor, Auxin response factors (ARF) and Myb transcription factors, cleaved by 6 known miRNA families and 6 predicted candidates, were found to be involved in regulating fruit senescence. The present study provided valuable information for understanding the quick senescence of strawberry fruit, and offered a foundation for studying the miRNA-mediated senescence of non-climacteric fruits.

Neutral Helium multiplets, He I* λλ3189, 3889, 10830 are very useful diagnostics to the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of He I* detections have been reported. Using a newly developed method, we detected He I*λ3889 absorption line in 101 sources of a well-defined sample of 285 Mg II BAL quasars selected from SDSS DR5. This has increased the number of He I* BAL quasars by more than one order of magnitude. We further detected He I*λ3189 in 50% (52/101) quasars in the sample. The detection fraction of He I* BALs in Mg II BAL quasars is ∼35% as a whole, and increases dramatically with increasing spectral signal-to-noise ratios, from ∼18% at S/N ≤ 10 to ∼93% at S/N ≥ 35. This suggests that He I* BALs could be detected in most Mg II LoBAL quasars, provided spectra S/N is high enough. Such a surprisingly high He I* BAL fraction is actually predicted from photo-ionization calculations based on a simple BAL model. The result indicates that He I* absorption lines can be used to search for BAL quasars at low-z, which cannot be identified by ground-based optical spectroscopic survey with commonly seen UV absorption lines. Using He I* λ3889, we discovered 19 BAL quasars at z < 0.3 from available SDSS spectral database. The fraction of He I* BAL quasars is similar to that of LoBAL objects.

In this paper we present an analysis of absorption line variability in mini-BAL quasar LBQS 1206+1052. The SDSS spectrum demonstrates that the absorption troughs can be divided into two components of blueshift velocities of ∼700 km s −1 and ∼1400 km s −1 relative to the quasar rest-frame. The former component shows rare Balmer absorption, which is an indicator of high density absorbing gas, thus the quasar is worth followup spectroscopic observations. Our follow-up optical and near-infrared spectra using MMT, YFOSC, TripleSpec and DBSP reveal that the strengths of the absorption lines vary for both of the two components, while the velocities do not change. We reproduce all of the spectral data by assuming that only the ionization state of the absorbing gas is variable and that all other physical properties are invariable. The variation of ionization is consistent with the variation of optical continuum from the V-band lightcurve. Additionally, we can not interpret the data by assuming that the variability is due to a movement of the absorbing gas. Therefore, our analysis strongly indicates that the absorption line variability in LBQS 1206+1052 is photoionization-driven. As shown from photo-ionization simulations, the absorbing gas with blueshift velocity of ∼700 km s −1 has a density in the range of 10 9 to 10 10 cm −3 and a distance of ∼1 pc, and the gas with blueshift velocity of ∼1400 km s −1 has a density of 10 3 cm −3 and a distance of ∼1 kpc.

No abstract