A High-Throughput Method for Screening Arabidopsis Mutants with Disordered Abiotic Stress-Induced Calcium Signal

It is established that different stresses cause signal-specific changes in cellular Ca2 ~ level, which function as messengers in modulating diverse physiological processes. These calcium signals are important for stress adaptation. Though numbers of downstream components of calcium signal cascades have been identified, upstream events in calcium signal remain elusive, specifically components required l＇~~r calcium signal generation due to the lack of high-throughput genetic assay. Here, we report the development of an easy and efficient method in a forward genetic screen for Ca2＋ signals-deficient mutants in Arahidopsis thaliana. Using this method, 121 mutants with disordered NaCI- and H=O2-induced Ca2＋ signals are isolated.

Directed Evolution of Insoluble Arabidopsis thaliana Zeta Class Glutathione S-Transferase Mutants for Higher Solubility in Escherichia coli

Expression of recombinant protein in Escherichia coli （E.coli） is generally considered as one of the ideal systems to produce proteins for industrial production.However,the majority of proteins usually fail to fold into their native state and accumulate as insoluble inclusion bodies with no biological activity in E.coli（Yang et al.,2003）.

ARF2 coordinates with PLETHORAs and PINs to orchestrate ABA-mediated root meristem activity in Arabidopsis

Multiple hormones, including abscisic acid（ABA） and auxin, regulate cell division and differentiation of Arabidopsis root meristems. AUXIN RESPONSE FACTOR2（ARF2） functions as a negative regulator of ABA responses, as seed germination and primary root growth of arf2 mutants are hypersensitive to ABA. In this study, we found that ABA treatment reduced the expression levels of the PIN-FORMEDs（PIN） auxin efflux carriers, PIN1, PIN3,PIN4, and PIN7, to a greater extent in the root meristems of arf2-101 mutant than in the wild type. Also, arf2-101 pin1 and arf2-101 pin4 double mutants show less ABA-induced inhibition of root meristem activity than the arf2-101 mutants. Furthermore, ARF2 positively mediates the transcripts of transcription factor PLETHORA 1（PLT1）gene but negatively mediates PLT2 at protein level in root meristems. Using a dexamethasone（DEX）-inducible transgenic line, Pro35S：PLT2-GR, we showed that PLT2 greatly promotes cell division and completely inhibits cell differentiation in root meristems of the arf2-101 mutant once PLT2 is induced by DEX, which can be partially reversed by ABA treatment, suggesting that ABA regulates root meristem activity in both ARF2-dependent and independent pathways. Our results uncover a complex regulatory architecture in which ARF2 coordinates with PLTs and PINs to orchestrate ABA-mediated regulation of root meristem activity in Arabidopsis.

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.

OST1 phosphorylates ICE1 to enhance plant cold tolerance

Low temperature is one of the most important environmental stresses that affect plant survival,growth and development.In response to cold stress,hundreds of genes are upor down-regulated in plants[1].The C-repeat binding factor（CBF）regulon is the best-understood cold-responsive transcriptional module[1].In Arabidopsis,there are three CBF genes,i.e.,CBF1,CBF2 and CBF3.They are rapidly.