Tracking and Monitoring Leaf Development, Coupling Law and Regulation Techniques during Flowering Period of Hybrid Foxtail Millet (<i>Setaria italica</i>(L.) P. Beauv.) Parental Lines

The determining factor of Setaria italica (L.) P. Beauv. is the coupling of its flowering stage and outcrossing rate which leads to low and unstable seed yields in self-pollinated foxtail millet hybrids and thereby limits their large-scale application. In this study, Datong 27, Datong 29 and gu 83 were screened and identified through meticulous observations of their pollination habitats. High exposure rate, degree of exposure and plump of stigma are good factors to accept foreign pollen. Datong 27 and Datong 29 have some additional characteristics, such as long filaments and exposed and full anthers that contain a large amount of pollen. We transformed into a series of stigma-exposed and plump sterile lines that easily accepted exotic pollen. New restorer lines with anthers that were full of powder and exhibited quick recovery, which improved the parental lines’ heterosexual characteristics. By tracking and monitoring the leaf development of the new sterile and restorer lines, a coupling law of leaf development was determined and a series of flowering control measures were formulated. These factors ensured that the parental lines encounter one another during the flowering stage. By utilizing fertilizer and water, the vitality of the female stigma, amount of powder scattered and powder loosening time were prolonged, which increased hybrid seed yields from 1500 to 3000 kg/hm2. These findings were helpful in resolving the technical problems of seed production that restricted the propagation of foxtail millet hybrids and supporting future large-scale applications.

Regulation of Flowering Time by MicroRNAs

The shoot apical meristem（SAM） continuously produces lateral organs in plants.Based on the identity of the lateral organs,the life cycle of a plant can be divided into two phases： vegetative and reproductive.The SAM produces leaves during the vegetative phase,whereas it gives rise to flowers in the reproductive phase（reviewed in Poethig,2003）.The floral transition,namely the switch from vegetative to reproductive growth,

Arabidopsis PWWP domain proteins mediate H_3K_(27) trimethylation on FLC and regulate flowering time

LHP1 mediates recruitment of the PRC2 histone methyltransferase complex to chromatin and thereby facilitates maintenance of H3K27me3 on FLC, a key flowering repressor gene. Here, we report that the PWWP domain proteins （PDPs） interact with FVE and MSI5 to suppress FLC expression and thereby promote flowering. We demonstrated that FVE, MSI5, and PDP3 were co-purified with LHP1. The H3K27me3 level on FLC was decreased in the pdp mutants as welt as in the fve/ msi5 double mutant. This study suggests that PDPs function together with FVE and MSI5 to regulate the function of the PRC2 complex on FLC.

Arabidopsis SUMO protease ASP1 positively regulates flowering time partially through regulating FLC stability

The initiation of flowering is tightly regulated by the endogenous and environment signals, which is crucial for the reproductive success of flowering plants. It is well known that autonomous and vernalization pathways repress transcription of FLOWERING LOCUS C（FLC）, a focal floral repressor, but how its protein stability is regulated remains largely unknown. Here, we found that mutations in a novel Arabidopsis SUMO protease 1（ASP1） resulted in a strong late-flowering phenotype under long-days, but to a lesser extent under short-days. ASP1 localizes in the nucleus and exhibited a SUMO protease activity in vitro and in vivo. The conserved Cys-577 in ASP1 is critical for its enzymatic activity, as well as its physiological function in the regulation of flowering time. Genetic and gene expression analyses demonstrated that ASP1 promotes transcription of positive regulators of flowering, such as FT,SOC1 and FD, and may function in both CO-dependent photoperiod pathway and FLC-dependent pathways.Although the transcription level of FLC was not affected in the loss-of-function asp1 mutant, the protein stability of FLC was increased in the asp1 mutant. Taken together, this study identified a novel bona fide SUMO protease, ASP1,which positively regulates transition to flowering at least partly by repressing FLC protein stability.

SUMO E3 Ligases GmSIZ1a and GmSIZ1b regulate vegetative growth in soybean

SIZ1 is a small ubiquitin-related modifier（SUMO） E3 ligase that mediates post-translational SUMO modification of target proteins and thereby regulates developmental processes and hormonal and environmental stress responses in Arabidopsis. However,the role of SUMO E3 ligases in crop plants is largely unknown. Here, we identified and characterized two Glycine max（soybean） SUMO E3 ligases, GmSIZ1a and GmSIZ1b. Expression of GmSIZ1a and GmSIZ1b was induced in response to salicylic acid（SA）, heat, and dehydration treatment, but not in response to cold, abscisic acid（ABA）, and Na Cl treatment. Although GmSIZ1a was expressed at higher levels than GmSIZ1b, both genes encoded proteins with SUMO E3 ligase activity in vivo.Heterologous expression of GmSIZ1a or GmSIZ1b rescued the mutant phenotype of Arabidopsis siz1-2, including dwarfism, constitutively activated expression of pathogen-related genes, and ABA-sensitive seed germination.Simultaneous downregulation of GmSIZ1a and GmSIZ1b（GmSIZ1a/b） using RNA interference（RNAi）-mediated gene silencing decreased heat shock-induced SUMO conjugation in soybean. Moreover, GmSIZ1 RNAi plants exhibited reduced plant height and leaf size. However,unlike Arabidopsis siz1-2 mutant plants, flowering time and SA levels were not significantly altered in GmSIZ1 RNAi plants. Taken together, our results indicate that GmSIZ1a and GmSIZ1b mediate SUMO modification and positively regulate vegetative growth in soybean.