Effect of tall-grass invasion on the flowering-related functional pattern of submediterranean hay-meadows

Several studies demonstrated that abandonment changes the functional composition of grasslands; nevertheless, little is known about the effects of grassland abandonment on the flowering-related functional pattern. We hypothesized that invasion by tall grasses affects this pattern. We counted the number of flowering shoots per species at five times during the growing season, in 80 plots placed in mown and in abandoned grasslands (central Apennines), and assessed the differences in the trait composition of flowering species between the two treatments. The selected traits were linked to resource acquisition and stress tolerance strategies. Our results indicated that abiotic environmental control is prevalent in determining the phenological pattern in both conditions and in accordance with the phenological “mid-domain hypothesis”. We demonstrated that when the dominant species is a tall grass with competitive behaviour, the magnitude of this phenomenon is amplified due to the abiotic changes yielded by the tall grass invasion. Indeed, in the central and late phases of the growing season (when invasive tall grasses are growing and blooming), abandoned grasslands were marked by a set of traits devoted to stress tolerance or underlying a long reproductive cycle or linked to competition for light.     

Abundance of mRNAs encoding HMG1/HMG2 class high-mobility-group DNA-binding proteins are differentially regulated in cotyledons of Pharbitis nil

The abundance of an mRNA encoding an HMG1/2 protein from Pharbitis nil (HMG1) has been previously shown to be regulated by light and an endogenous rhythm in cotyledons. A second Pharbitis nil HMG cDNA (HMG2) was characterized. The sequence of HMG2 was 82% and 86% identical to HMG1 at the nucleotide and amino acid level, respectively. As with HMG1, HMG2 mRNA was detected in all vegetative tissues and was most abundant in roots. However, unlike HMG1, HMG2 mRNA abundance did not increase upon transfer of cotyledons to darkness and did not exhibit regulation by an endogenous circadian rhythm when maintained in continuous darkness over a 68 h period. Similarly, while the abundance of HMG1 mRNA during a dark period that induced photoperiodically controlled flowering was dramatically affected by brief light exposure (night break), this treatment had no effect on HMG2 mRNA abundance. Collectively, these data are consistent with a role of HMG1 in contributing to the circadian-regulated and/or dark-regulated gene expression with constitutive expression of HMG2 playing a housekeeping role in the general regulation of gene expression in Pharbitis nil cotyledons.     

Reduced generation time of apple seedlings to within a year by means of a plant virus vector: a new plant‐breeding technique with no transmission of genetic modification to the next generation

Fruit trees have a long juvenile phase. For example, the juvenile phase of apple (Malus × domestica) generally lasts for 5–12 years and is a serious constraint for genetic analysis and for creating new apple cultivars through cross‐breeding. If modification of the genes involved in the transition from the juvenile phase to the adult phase can enable apple to complete its life cycle within 1 year, as seen in herbaceous plants, a significant enhancement in apple breeding will be realized. Here, we report a novel technology that simultaneously promotes expression of Arabidopsis FLOWERING LOCUS T gene (AtFT) and silencing of apple TERMINAL FLOWER 1 gene (MdTFL1‐1) using an Apple latent spherical virus (ALSV) vector (ALSV‐AtFT/MdTFL1) to accelerate flowering time and life cycle in apple seedlings. When apple cotyledons were inoculated with ALSV‐AtFT/MdTFL1 immediately after germination, more than 90% of infected seedlings started flowering within 1.5–3 months, and almost all early‐flowering seedlings continuously produced flower buds on the lateral and axillary shoots. Cross‐pollination between early‐flowering apple plants produced fruits with seeds, indicating that ALSV‐AtFT/MdTFL1 inoculation successfully reduced the time required for completion of the apple life cycle to 1 year or less. Apple latent spherical virus was not transmitted via seeds to successive progenies in most cases, and thus, this method will serve as a new breeding technique that does not pass genetic modification to the next generation.     

Successful crossings with early flowering transgenic poplar: interspecific crossings,but not transgenesis,promoted aberrant phenotypes in offspring

In forest tree species, the reproductive phase is reached only after many years or even decades of juvenile growth. Different early flowering systems based on the genetic transfer of heat‐shock promoter driven flowering‐time genes have been proposed for poplar; however, no fertile flowers were reported until now. Here, we studied flower and pollen development in both HSP::AtFT and wild‐type male poplar in detail and developed an optimized heat treatment protocol to obtain fertile HSP::AtFT flowers. Anthers from HSP::AtFT poplar flowers containing fertile pollen grains showed arrested development in stage 12 instead of reaching phase 13 as do wild‐type flowers. Pollen grains could be isolated under the binocular microscope and were used for intra‐ and interspecific crossings with wild‐type poplar. F1‐seedlings segregating the HSP::AtFT gene construct according to Mendelian laws were obtained. A comparison between intra‐ and interspecific crossings revealed that genetic transformation had no detrimental effects on F1‐seedlings. However, interspecific crossings, a broadly accepted breeding method, produced 47% seedlings with an aberrant phenotype. The early flowering system presented in this study opens new possibilities for accelerating breeding of poplar and other forest tree species. Fast breeding and the selection of transgene‐free plants, once the breeding process is concluded, can represent an attractive alternative even under very restrictive regulations.     

Growth period QTL-allele constitution of global soybeans and its differential evolution changes in geographic adaptation versus maturity group extension

Soybean (Glycine max (L.) Merr.) has been disseminated globally as a photoperiod/temperature-sensitive crop with extremely diverse days to flowering (DTF) and days to maturity (DTM) values. A population with 371 global varieties covering 13 geographic regions and 13 maturity groups (MGs) was analyzed for its DTF and DTM QTL-allele constitution using restricted two-stage multi-locus genome-wide association study (RTM-GWAS). Genotypes with 20 701 genome-wide SNPLDBs (single-nucleotide polymorphism linkage disequilibrium blocks) containing 55 404 haplotypes were observed, and 52 DTF QTLs and 59 DTM QTLs (including 29 and 21 new ones) with 241 and 246 alleles (two to 13 per locus) were detected, explaining 84.8% and 74.4% of the phenotypic variance, respectively. The QTL-allele matrix characterized with all QTL-allele information of each variety in the global population was established and subsequently separated into geographic and MG set submatrices. Direct comparisons among them revealed that the genetic adaptation from the origin to geographic subpopulations was characterized by new allele/new locus emergence (mutation) but little allele exclusion (selection), while that from the primary MG set to emerged early and late MG sets was characterized by allele exclusion without allele emergence. The evolutionary changes involved mainly 72 DTF and 71 DTM alleles on 28 respective loci, 10–12 loci each with three to six alleles being most active. Further recombination potential for faster maturation (12–21 days) or slower maturation (14–56 days) supported allele convergence (recombination) as a constant genetic factor in addition to migration (inheritance). From the QTLs, 44 DTF and 36 DTM candidate genes were annotated and grouped respectively into nine biological processes, indicating multi-functional DTF/DTM genes are involved in a complex gene network. In summary, we identified QTL-alleles relatively thoroughly using RTM-GWAS for direct matrix comparisons and subsequent analysis.     

植物BBX转录因子基因家族的研究进展

转录因子在调控植物生长、发育及环境适应性等方面发挥重要作用。具有B-box结构域的一类锌指结构转录因子称为BBX,它们通过调控基因转录,与同类或其他转录因子的互作参与植物光形态建成、花发育、避荫效应、植物信号转导以及非生物和生物逆境响应等。文中从BBX蛋白结构、分类以及其功能方面对该类转录因子在植物中的作用进行了综述。     

Ambient temperature signaling in plants: An emerging field in the regulation of flowering time

Plants show remarkable developmental plasticity to survive in a continually changing environment. One example is their capability to adjust flowering time in response to environmental changes. Ambient growth temperature, which is strongly affected by global temperature changes, has a profound effect on flowering time. However, those effects have been largely ignored in research. Recent molecular genetic studies ofArabidopsis as a model system have implicated several genes, and have identified a molecular mechanism underlying the responses of plants to changes in ambient temperature. Here, we describe recent discoveries related to ambient temperature signaling and the control of flowering time inArabidopsis. We also discuss current perspectives on how plants sense and respond to such changes.     

Flowering requirements of Scandinavian Festuca pratensis

Flowering requirements of three Scandinavian cultivars of Festuca pratensis Huds, have been studied in controlled environments. At 3 and 6°C, primary induction was independent of photoperiod, while short days (8 h) were more effective than long days (24 h) at higher temperatures. The critical temperature for induction was about 15°C in short days and about 12°C in long days. Saturation of induction required 18–20 weeks of exposure to optimal conditions. At temperatures below 12°C both induction and initiation of inflorescence primordia took place in long days, while a transition to long days was required for inflorescence initiation after primary induction in short days. A minimum of 8 long-day cycles were required for flowering of plants primary induced in short days and saturation of flowering required more than 16 cycles. The critical photoperiod for secondary induction was about 13 h. High temperature (21°C) had some devernalization effect in primary induced plants, suppressing flowering compared with 15°C.