In order to better explore the maintenance mechanisms of biodiversity,data collected from a 40-ha undisturbed Pinus forest were applied to the Individual SpecieseArea Relationship model (ISAR) to determine distribution patterns for species richness.The ecological processes influencing species abundance distribution patterns were assessed by applying the same data set to five models:a LogNormal Model (LNM),a Broken Stick Model (BSM),a Zipf Model (ZM),a Niche Preemption Model (NPM),and a Neutral Model (NM).Each of the five models was used at six different sampling scales (10 m×10 m,20 m×20 m,40 m×40 m,60 m×60 m,80 m×80 m,and 100 m×100 m).Model outputs showed that:(1) Accumulators and neutral species strongly influenced species diversity,but the relative importance of the two types of species varied across spatial scales.(2) Distribution patterns of species abundance were best explained by the NPM at small scales (10 me20 m),whereas the NM was the best fit model at large spatial scales.(3) Species richness and abundance distribution patterns appeared to be driven by similar ecological processes.At small scales,the niche theory could be applied to describe species richness and abundance,while at larger scales the neutral theory was more applicable.
The turnip (Brassica rapa var.rapa) is a biennial crop that is planted in late summer/early fall and forms fleshy tubers for food in temperate regions.The harvested tubers then overwinter and are planted again the next spring for flowering and seeds.FLOWERING LOCUS C (FLC) is a MADS-box transcription factor that acts as a major repressor of floral transition by suppressing the flowering promoters FT and SOC1.Here we show that vernalization effectively represses tuber formation and promotes flowering in Tibetan turnip.We functionally characterized four FLC homologues (BrrFLC1, FLC2,FLC3,and FLC5),and found that BrrFLC2 and BrrFLC1 play a major role in repressing flowering in turnip and in transgenic Arabidopsis.In contrast,tuber formation was correlated with BrrFLC1 expression in the hypocotyl and was repressed under cold treatment following the quantitative downregulation of BrrFLC1.Grafting experiments of non-vernalized and vernalized turnips revealed that vernalization independently suppressed tuberization in the tuber or hypocotyl of the rootstock or scion,which occurred in parallel with the reduction in BrrFLC1 activity.Together,our results demonstrate that the Tibetan turnip is highly responsive to cold exposure,which is associated with the expression levels of BrrFLC genes.
Oligopeptide transporters (OPTs) encode integral membrane-localized proteins and have a broad range of substrate transport capabilities.Here,28 BrrOPT genes were identified in the turnip.Phylogenetic analyses revealed two well-supported clades in the OPT family,containing 15 BrrOPTs and 13 BrrYSLs. The exon/intron structure of OPT clade are conserved but the yellow stripe-like (YSL) clade was different. The exon/intron of the YSL clade possesses structural differences,whereas the YSL class motifs structure are conserved.The OPT genes are distributed unevenly among the chromosomes of the turnip genome. Phylogenetic and chromosomal distribution analyses revealed that the expansion of the OPT gene family is mainly attributable to segmental duplication.For the expression profiles at different developmental stages,a comprehensive analysis provided insights into the possible functional divergence among members of the paralog OPT gene family.Different expression levels under a variety of ion deficiencies also indicated that the OPT family underwent functional divergence during long-term evolution. Furthermore,BrrOPT8.1,BrrYSL1.2,BrrYSL1.3,BrrYSL6 and BrrYSL9 responded to Fe (Ⅱ) treatments and BrrYSL7 responded to calcium treatments,BrrYSL6 responded to multiple treatments in root,suggesting that turnip OPTs may be involved in mediating cross-talk among different ion deficiencies.Our data provide important information for further functional dissection of BrrOPTs,especially in transporting metal ions and nutrient deficiency stress adaptation.
Pleiotropic drug resistance (PDR) transporters are widely distributed membrane proteins catalyzing the export or import of a diverse array of molecules,and are involved in many plant responses to biotic and abiotic stresses.However,it is unclear whether PDRs are involved in Nicotiana attenuata resistance to the necrotic fungal pathogen Alternaria alternata.In this study,transcriptional levels of both NaPDR1 and NaPDR1-like were highly induced in N.attenuata leaves after A.alternata inoculation.Interestingly, silencing NaPDR1 or NaPDR1-like individually had little effect on N.attenuata resistance to A.alternata; however,when both genes were co-silenced plants became highly susceptible to the fungus,which was associated with elevated JA and ethylene responses.Neither NaPDR1 nor NaPDR1-like was significantly elicited by exogenous treatment with methyl jasmonate (MeJA),whereas both were highly induced by ethylene.The elicitation levels of both genes by A.alternata were significantly reduced in plants with impaired JA or ethylene signaling pathways.Thus,we conclude that both NaPDR1 and NaPDR1-like function redundantly to confer resistance against A.alternata in N.attenuata,and the elicitation of the transcripts of both genes by the fungus is partially dependent on ethylene and jasmonate signaling.