Abiotic and biotic stresses are major limiting factors of crop yields and cause billions of dollars of losses annually around the world. It is hoped that understanding at the molecular level how plants respond to adverse conditions and adapt to a changing environment will help in developing plants that can better cope with stresses. Acquisition of stress tolerance requires orchestration of a multitude of biochemical and physiological changes, and most of these depend on changes in gene expression. Research during the last two decades has established that different stresses cause signal-specific changes in cellular Ca 2+ level, which functions as a messenger in modulating diverse physiological processes that are important for stress adaptation. In recent years, many Ca 2+ and Ca 2+ /calmodulin (CaM) binding transcription factors (TFs) have been identified in plants. Functional analyses of some of these TFs indicate that they play key roles in stress signaling pathways. Here, we review recent progress in this area with emphasis on the roles of Ca 2+ -and Ca 2+ /CaMregulated transcription in stress responses. We will discuss emerging paradigms in the field, highlight the areas that need further investigation, and present some promising novel high-throughput tools to address Ca 2+ -regulated transcriptional networks.

Background: Kinesins constitute a superfamily of microtubule motor proteins that are found in eukaryotic organisms. Members of the kinesin superfamily perform many diverse cellular functions such as transport of vesicles and organelles, spindle formation and elongation, chromosome segregation, microtubule dynamics and morphogenesis. Only a few kinesins have been characterized in plants including Arabidopsis thaliana. Because of the diverse cellular functions in which kinesins are involved, the number, types and characteristics of kinesins present in the Arabidopsis genome would provide valuable information for many researchers.

The generation of mature mRNAs from most genes (about 80%-90%) in autotrophic eukaryotes requires the removal of noncoding sequences (introns) and splicing of the coding regions (exons; Labadorf et al., 2010). During splicing in some precursor messenger RNAs (pre-mRNAs), the same splice sites are always used, referred to as constitutive splicing (CS), resulting in a single transcript from a gene. However, from many pre-mRNAs, multiple mature mRNAs are generated from a single gene by alternative splicing (AS), where different combinations of splice sites are used. Both CS and AS are critical to the proper expression of intron-containing genes. Recent transcriptome-wide analysis of AS using high-throughput sequencing indicates that pre-mRNAs from up to 42% of introncontaining genes in Arabidopsis (Arabidopsis thaliana; Filichkin et al., 2010) and about 48% in rice (Oryza sativa; Lu et al., 2010) are alternatively spliced, whereas about 95% of human genes are alternatively spliced (Pan et al., 2008). In addition to pre-mRNAs, some primary microRNAs (pri-miRNAs) are also subject to CS and AS (Hirsch et al., 2006;Szarzynska et al., 2009;Mica et al., 2010). AS increases the protein-coding capacity of a genome and generates functionally different proteins from the same gene (Reddy, 2007). AS results in protein isoforms with loss or gain of function and altered subcellular localization, protein stability, and/or posttranslational modifications. Furthermore, AS plays an important role in gene regulation through regulated unproductive splicing and translation, leading to RNA degradation by mRNA surveillance mechanisms, differential recruitment of mRNAs to ribosomes, or translatability of splice variants (Kurihara et al., 2009;Licatalosi and Darnell, 2010;Palusa and Reddy, 2010). Numerous spliceosomal proteins either promote or suppress splicing by interacting with splicing regulatory elements on the pre-mRNAs. In recent years, the localization and dynamics of some splicing regulators in plants have been analyzed using a variety of approaches. This review summarizes the current status of research in this area, with emphasis on RNAbinding proteins (RBPs) that are involved in splicing regulation, discusses open questions, and presents some approaches to address these questions. SPLICING REGULATORSpre-mRNAs splicing takes place cotranscriptionally in the spliceosome, a large multicomponent complex composed of small nuclear RNAs (snRNAs) and about 170 proteins, many of which are involved in the regulation of splicing (Wahl et al., 2009;Valadkhan and Jaladat, 2010). The composition of the human and yeast spliceosome has been analyzed in great detail (Wahl et al., 2009); however, information on plant splicing has been scarce, as no in vitro assembly of a functional plant spliceosome has been possible to date. A detailed search for Arabidopsis orthologs of the human spliceosome proteome revealed that most splicing factors are present in the Arabidopsis genome, indicating a similar complexity (Barta et al., 2011). Interestingly, m...