Preliminary Expression Analysis of the OSCA Gene Family in Maize and Their Involvement in Temperature Stress.

Hyperosmolality-gated calcium-permeable channels (OSCA) are characterized as an osmosensor in plants; they are able to recognize and respond to exogenous and endogenous osmotic changes, and play a vital role in plant growth and adaptability to environmental stress. To explore the potential biological functions of OSCAs in maize, we performed a bioinformatics and expression analysis of the ZmOSCA gene family. Using bioinformatics methods, we identified twelve OSCA genes from the genome database of maize. According to their sequence composition and phylogenetic relationship, the maize OSCA family was classified into four groups (Ⅰ, Ⅱ, Ⅲ, and Ⅳ). Multiple sequence alignment analysis revealed a conserved DUF221 domain in these members. We modeled the calcium binding sites of four OSCA families using the autodocking technique. The expression profiles of ZmOSCA genes were analyzed in different tissues and under diverse abiotic stresses such as drought, salt, high temperature, and chilling using quantitative real-time PCR (qRT-PCR). We found that the expression of twelve ZmOSCA genes is variant in different tissues of maize. Furthermore, abiotic stresses such as drought, salt, high temperature, and chilling differentially induced the expression of twelve ZmOSCA genes. We chose ZmOSCA2.2 and ZmOSCA2.3, which responded most strongly to temperature stress, for prediction of protein interactions. We modeled the calcium binding sites of four OSCA families using autodocking tools, obtaining a number of new results. These results are helpful in understanding the function of the plant OSCA gene family for study of the molecular mechanism of plant osmotic stress and response, as well as exploration of the interaction between osmotic stress, high-temperature stress, and low-temperature stress signal transduction mechanisms. As such, they can provide a theoretical basis for crop breeding.

Biological function of calcium-sensing receptor (CAS) and its coupling calcium signaling in plants.

The calcium-sensing receptor (CAS), as a chloroplast thylakoid membrane protein, is involved in the process of external Ca2+-induced cytosolic Ca2+ increase in plants. However, the underlying mechanism regulating this process is lacking. Furthermore, recent evidence suggests that CAS may perform additional roles in plants. Here, we provided an update covering the multiple roles of CAS in stomatal movement regulation and Ca2+ signaling in plants. We also analyzed the possible phosphorylation mechanism of CAS by light and discuss the role of CAS in abiotic stress (drought, salt stress) and biotic stresses (plant immune signaling). Finally, we proposed a perspective for future experiments that are required to fill gaps in our understanding of the biological function of CAS in plants.

Arabidopsis CIB3 regulates photoperiodic flowering in an FKF1-dependent way.

Arabidopsis cryptochrome 2 (CRY2) and FLAVIN-BINDING, KELCH REPEAT, and F-BOX 1 (FKF1) are blue light receptors mediating light regulation of growth and development, such as photoperiodic flowering. CRY2 interacts with a basic helix-loop-helix transcription factor CIB1 in response to blue light to activate the transcription of the flowering integrator gene FLOWERING LOCUS T (FT). CIB1, CIB2, CIB4, and CIB5 function redundantly to promote flowering in a CRY2-dependent way and form various heterodimers to bind to the noncanonical E-box sequence in the FT promoter. However, the function of CIB3 has not been described. We discovered that CIB3 promotes photoperiodic flowering independently of CRY2. Moreover, CIB3 does not interact with CRY2 but interacts with CIB1 and functions synergistically with CIB1 to promote the transcription of the GI gene. FKF1 is required for CIB3 to promote flowering and enhances the CIB1-CIB3 interaction in response to blue light.

Comparative proteomic analysis of differentially expressed proteins in ß-aminobutyric acid enhanced Arabidopsis thaliana tolerance to simulated acid rain.

Acid rain is a worldwide environmental issue that has seriously destroyed forest ecosystems. As a highly effective and broad-spectrum plant resistance-inducing agent, ß-aminobutyric acid could elevate the tolerance of Arabidopsis when subjected to simulated acid rain. Using comparative proteomic strategies, we analyzed 203 significantly varied proteins of which 175 proteins were identified responding to ß-aminobutyric acid in the absence and presence of simulated acid rain. They could be divided into ten groups according to their biological functions. Among them, the majority was cell rescue, development and defense-related proteins, followed by transcription, protein synthesis, folding, modification and destination-associated proteins. Our conclusion is ß-aminobutyric acid can lead to a large-scale primary metabolism change and simultaneously activate antioxidant system and salicylic acid, jasmonic acid, abscisic acid signaling pathways. In addition, ß-aminobutyric acid can reinforce physical barriers to defend simulated acid rain stress.

Expression of five AtHsp90 genes in Saccharomyces cerevisiae reveals functional differences of AtHsp90s under abiotic stresses.

The genome of Arabidopsis thaliana contains seven Hsp90 family genes. Three organellar and two cytosolic AtHsp90 isoforms were characterized by functionally expressing them in a temperature-sensitive Hsp90 mutant and a conditional Hsp90-null mutant of Saccharomyces cerevisiae. The cytosolic AtHsp90-1 and AtHsp90-2 showed function similar to that of yeast in chaperoning roles; they could support the growth of yeast mutants at both permissive and non-permissive temperature. Neither the full-length nor mature forms of chloroplast-located AtHsp90-5, mitochondria-located AtHsp90-6 and endoplasmic reticulum (ER)-located AtHsp90-7 could complement the yeast Hsp90 proteins. The cytosolic AtHsp90s could stabilize the biomembrane of the temperature-sensitive Hsp90 mutant strains under stress conditions, while the organellar AtHsp90s could not protect the biomembrane of the temperature-sensitive Hsp90 mutant strains. Yeast two-hybrid results showed that either pre-protein or mature forms of organellar AtHsp90s could interact with cofactors cpHsp70, Hsp70, Hsp70t-2, Cyp40, p23 and a substrate protein of NOS, while cytosolic AtHsp90s could not interact with them. These results suggest that organellar and cytosolic AtHsp90s possibly work through different molecular mechanisms in forming chaperone complexes and performing their functional roles.

[Selection and identification of salt-tolerant variants of Taraxacum officinale].

In order to obtain salt-tolerant variant plants of Dandelion (Taraxacum officinale Weber), the leaf discs were excised from 20 to 30-day old seedlings to produce callus, then the induced calli were transferred to selection mediums containing 1.5% NaCl. After regenerating and rooting, these salt-tolerant calli finally developed into 12 variant plantlets. Compared with the wild-type, these regenerated plants produced more trichomes on their leaves, and had larger leaves and shorter petioles. Additionally, the dumpy roots and an approximately 2-cm bract in middle parts of the floricanes were clearly observed in these salt-tolerant plants. By RAPD (Random Amplified Polymorphic DNA) and SDS-PAGE analysis, these salt-tolerant plants showed differences from the control at DNA and protein levels. With 1.5% NaCl treatment, the antioxidant enzyme activity, proline content, and flavonoid concentration were higher in these salt-tolerant plants, whereas maloaldehyde concentration was significantly lower. Salt-tolerant lines of T. officinale showed stronger anti-oxidative activity and higher flavonoid contents.

A protein extraction method compatible with proteomic analysis for the euhalophyte Salicornia europaea.

Protein extraction from plants like the halophyte Salicornia europaea has been problematic using standard protocols due to high concentrations of salt ions in their cells. We have developed an improved method for protein extraction from S. europaea, which allowed us to remove interfering compounds and salt ions by including the chemicals borax, polyvinylpolypyrrolidone, and phenol. The comparative study of this method with several other protocols using NaCl-treated S. europaea shoots demonstrated that this method gave the best distinction of proteins on 2-DE gels. This protocol had a wide range of applications as high yields and good distinction of 1-DE gels for proteins isolated from twelve other plants were rendered. In addition, we reported results of 2-DE using the recalcitrant tissue of the S. europaea roots. We also demonstrated that this protocol is compatible with proteomic analysis as eight specific proteins generated by this method have been identified by MS. In conclusion, our newly developed protein extraction protocol is expected to have excellent applications in proteomic studies of halophytes.