Two-factor ANOVA of SSH and RNA-seq analysis reveal development-associated Pi-starvation genes in oilseed rape.

MAIN CONCLUSION: The 5-leaf-stage rape seedlings were more insensitive to Pi starvation than that of the 3-leaf-stage plants, which may be attributed to the higher expression levels of ethylene signaling and sugar-metabolism genes in more mature seedlings. Traditional suppression subtractive hybridization (SSH) and RNA-Seq usually screen out thousands of differentially expressed genes. However, identification of the most important regulators has not been performed to date. Here, we employed two methods, namely, a two-round SSH and two-factor transcriptome analysis derived from the two-factor ANOVA that is commonly used in the statistics, to identify development-associated inorganic phosphate (Pi) starvation-induced genes in Brassica napus. Several of these genes are related to ethylene signaling (such as EIN3, ACO3, ACS8, ERF1A, and ERF2) or sugar metabolism (such as ACC2, GH3, LHCB1.4, XTH4, and SUS2). Although sucrose and ethylene may counteract each other at the biosynthetic level, they may also work synergistically on Pi-starvation-induced gene expression (such as PT1, PT2, RNS1, ACP5, AT4, and IPS1) and root acid phosphatase activation. Furthermore, three new transcription factors that are responsive to Pi starvation were identified: the zinc-finger MYND domain-containing protein 15 (MYND), a Magonashi family protein (MAGO), and a B-box zinc-finger family salt-tolerance protein. This study indicates that the two methods are highly efficient for functional gene screening in non-model organisms.

Nitrogen and nitric oxide regulate Arabidopsis flowering differently.

Both nitrogen (N) and nitric oxide (NO) postpone plant flowering. However, we still don't know whether N and NO trigger the same signaling pathways leading to flowering delay. Our previous study found that ferredoxin NADP+ oxidoreductase (FNR1) and the blue-light receptor cryptochrome 1 (CRY1) are involved in nitrogen-regulated flowering-time control. However, NO-induced late-flowering does not require FNR1 or CRY1. Sucrose supply counteracts the flowering delay induced by NO. However high-N-induced late-flowering could not be reversed by 5% sucrose supplementation. The high nitrogen condition decreased the amplitudes of all transcripts of the circadian clock. While NO increased the amplitudes of circadian transcripts of CRY1, LHY (LATE ELONGATED HYPOCOTYL), CCA1 (CIRCADIAN CLOCK ASSOCIATED 1) and TOC1 (TIMING OF CAB EXPRESSION 1), but decreased the amplitudes of circadian transcripts of CO (CONSTANS) and GI (GIGANTEA). 5% sucrose supplementation reversed the declines in amplitudes of circadian transcripts of CO and GI after the NO treatment. NO induced S-nitrosation modification on oscillators CO and GI, but not on the other oscillators of the circadian clock. Sucrose supply interestingly reduced S-nitrosation levels of GI and CO proteins. Thus N and NO rely on overlapping but distinct signaling pathways on plant flowering.

[Tissue culture and rapid propagation of Phytolacca americana].

OBJECTIVE: To explore the technique of rapid propagation for Phytolacca americana. METHODS: Aseptic seedling were used as explants. RESULTS: The best explants were the stems from strong aseptic seedling. The optimal culture media were MS + NAA (0.2 mg/L) +6-BA (1.0 mg/L) for primarily culture, MS + NAA (0.2 mg/L) +6-BA (2.0 mg/L) for the induction of clustered shoots 1/2MS with NAA 0.4 mg/L for rooting. CONCLUSION: The propagating coefficient of Phytolacca americana can be improved by inducing the clustered shoots from aseptic seedling.

[Effects of drought stress on leaf gas exchange and chlorophyll fluorescence of Salvia miltiorrhiza].

Taking the seedlings of Salvia miltiorrhiza cv. Sativa (SA) and S. miltiorrhiza cv. Silcestris (SI) as test materials, this paper studied the effects of drought stress on their leaf gas exchange and chlorophyll fluorescence parameters. After 15 days of drought stress, the net photosynthetic rate (P(n)) and the maximal photochemical efficiency of PS II (F(v)/F(m)) of SA were decreased by 66.42% and 10.98%, whereas those of SI were decreased by 29.32% and 5.47%, respectively, compared with the control, suggesting that drought stress had more obvious effects on the P(n) and F(v)/F(m) of SA than of SI. For SI, the reduction of P, under drought stress was mainly due to stomatal limitation; while for SA, it was mainly due to non-stomatal limitation. Drought led to a decrease of leaf stomatal conductance (G(s)), but induced the increase of water use efficiency (WUE), non-photochemical quenching coefficient (q(N)), and the ratio of photorespiration rate to net photosynthetic rate (P(r)/P(n)), resulting in the enhancement of drought resistance. The increment of WUE, q(N), and P(r)/P(n) was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.