Tissue-specific, light-regulated and plastid-regulated expression of the single-copy nuclear gene encoding the chloroplast Rieske FeS protein of Arabidopsis thaliana

Single-molecule real-time sequencing of the full-length transcriptome of Halophila beccarii

Ecologically, Halophila beccarii Asch. is considered as a colonizing or a pioneer seagrass species and a “tiny but mighty” seagrass species, since it may recover quickly from disturbance generally. The use of transcriptome technology can provide a better understanding of the physiological processes of seagrasses. To date, little is known about the genome and transcriptome information of H. beccarii. In this study, we used single molecule real-time (SMRT) sequencing to obtain full-length transcriptome data and characterize the transcriptome structure. A total of 11,773 of the 15,348 transcripts were successfully annotated in seven databases. In addition, 1573 long non-coding RNAs, 8402 simple sequence repeats and 2567 transcription factors were predicted in all the transcripts. A GO analysis showed that 5843 transcripts were divided into three categories, including biological process (BP), cellular component (CC) and molecular function (MF). In these three categories, metabolic process (1603 transcripts), protein-containing complex (515 transcripts) and binding (3233 transcripts) were the primary terms in BP, CC, and MF, respectively. The major types of transcription factors were involved in MYB-related and NF-YB families. To the best of our knowledge, this is the first report of the transcriptome of H. beccarii using SMRT sequencing technology.

Enhanced Relative Electron Transport Rate Contributes to Increased Photosynthetic Capacity in Autotetraploid Pak Choi

Autopolyploids often show growth advantages over their diploid progenitors because of their increased photosynthetic activity; however, the underlying molecular basis of such mechanism remains elusive. In this study, we aimed to characterize autotetraploid pak choi (Brassica rapa ssp. chinensis) at the physiological, cellular and molecular levels. Autotetraploid pak choi has thicker leaves than its diploid counterparts, with relatively larger intercellular spaces and cell size and greater grana thylakoid height. Photosynthetic data showed that the relative electron transport rate (rETR) was markedly higher in autotetraploid than in diploid pak choi. Transcriptomic data revealed that the expressions of genes involved in 'photosynthesis' biological process and 'thylakoids' cellular component were mainly regulated in autotetraploids. Overall, our findings suggested that the increased rETR in the thylakoids contributed to the increased photosynthetic capacity of autotetraploid leaves. Furthermore, we found that the enhanced rETR is associated with increased BrPetC expression, which is likely altered by histone modification. The ectopic expression of BrPetC in Arabidopsis thaliana led to increased rETR and biomass, which were decreased in BrPetC-silenced pak choi. Autotetraploid pak choi also shows altered hormone levels, which was likely responsible for the increased drought resistance and the impaired powdery mildew resistance of this lineage. Our findings further our understanding on how autotetraploidy provides growth advantages to plants.

Feeding the world: improving photosynthetic efficiency for sustainable crop production

A number of recent studies have provided strong support demonstrating that improving the photosynthetic processes through genetic engineering can provide an avenue to improve yield potential. The major focus of this review is on improvement of the Calvin-Benson cycle and electron transport. Consideration is also given to how altering regulatory process may provide an additional route to increase photosynthetic efficiency. Here we summarize some of the recent successes that have been observed through genetic manipulation of photosynthesis, showing that, in both the glasshouse and the field, yield can be increased by >40%. These results provide a clear demonstration of the potential for increasing yield through improvements in photosynthesis. In the final section, we consider the need to stack improvement in photosynthetic traits with traits that target the yield gap in order to provide robust germplasm for different crops across the globe.

Overexpression of the RieskeFeS Protein Increases Electron Transport Rates and Biomass Yield

In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the Rieske FeS protein (PetC), a component of the cytochrome b₆f (cyt b₆f) complex. Increasing the levels of this protein resulted in concomitant increases in the levels of cyt f (PetA) and cyt b₆ (PetB), core proteins of the cyt b₆f complex. Interestingly, an increase in the levels of proteins in both the photosystem I (PSI) and PSII complexes also was seen in the Rieske FeS overexpression plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, overexpression of the Rieske FeS protein resulted in substantial and significant impacts on the quantum efficiency of PSI and PSII, electron transport, biomass, and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.

Simple Identification of TransgenicArabidopsisPlants Carrying a Single Copy of the Integrated Gene

Transgenic Arabidopsis thaliana plants carrying a single copy of integrated DNA can be identified by single-step genomic polymerase chain reaction. The reaction employs two sets of primer pairs with the same melting temperature that amplify the amplicons derived from the integrated T-DNA together with those from an endogenous single-copy gene as a reference. When the band intensity ratio is one, this means that the transgenic plants are carrying a single copy of the integrated gene per haploid.

Multiple Rieske proteins in prokaryotes: where and why?

Many microbial genomes have been sequenced in the recent years. Multiple genes encoding Rieske iron-sulfur proteins, which are subunits of cytochrome bc-type complexes or oxygenases, have been detected in many pro- and eukaryotic genomes. The diversity of substrates, co-substrates and reactions offers obvious explanations for the diversity of the low potential Rieske proteins associated with oxygenases, but the physiological significance of the multiple genes encoding high potential Rieske proteins associated with the cytochrome bc-type complexes remains elusive. For some organisms, investigations into the function of the later group of genes have been initiated. Here, we summarize recent finding on the characteristics and physiological functions of multiple high potential Rieske proteins in prokaryotes. We suggest that the existence of multiple high potential Rieske proteins in prokaryotes could be one way of allowing an organism to adapt their electron transfer chains to changing environmental conditions.

Plant immunophilins: functional versatility beyond protein maturation

Originally identified as the cellular targets of immunosuppressant drugs, the immunophilins encompass two ubiquitous protein families: the FK-506 binding proteins or FKBPs, and the cyclosporin-binding proteins or cyclophilins. Present in organisms ranging from bacteria to animals and plants, these proteins are characterized by their enzymatic activity; the peptidyl-prolyl cis-trans isomerization of polypeptides. Whilst this function is important for protein folding, it has formed the functional basis for more complex interactions between immunophilins and their target proteins. Beginning with a brief historical overview of the immunophilin family, and a representative illustration of the current state of knowledge that has accumulated for these proteins in diverse organisms, a detailed description is presented of the recent advances in the elucidation of the role of this ubiquitous protein family in plant biology. Though still in its infancy, investigation into the function of plant immunophilins has so far yielded interesting results--as a significant component of the chloroplast proteome, the abundance of immunophilins located in the thylakoid lumen suggests that these proteins may play important roles in this relatively uncharacterized subcellular compartment. Moreover, the importance of the complex multidomain immunophilins in functions pertaining to development is underscored by the strong phenotypes displayed by their corresponding mutants.

Solute transporters of the plastid envelope membrane

Plastids are metabolically extraordinarily active and versatile organelles that are found in all plant cells with the exception of angiosperm pollen grains. Many of the plastid-localized biochemical pathways depend on precursors from the cytosol and, in turn, many cytosolic pathways depend on the supply of precursor molecules from the plastid stroma. Hence, a massive traffic of metabolites occurs across the permeability barrier between plastids and cytosol that is called the plastid envelope membrane. Many of the known plastid envelope solute transporters have been identified by biochemical purification and peptide sequencing. This approach is of limited use for less abundant proteins and for proteins of plastid subtypes that are difficult to isolate in preparative amounts. Hence, the majority of plastid envelope membrane transporters are not yet identified at the molecular level. The availability of fully sequenced plant genomes, the progress in bioinformatics to predict membrane transporters localized in plastids, and the development of highly sensitive proteomics techniques open new avenues toward identifying additional, to date unknown, plastid envelope membrane transporters.

Analysis of Arabidopsis PsbQA gene expression in transgenic tobacco reveals differential role of its promoter and transcribed region in organ-specific and light-mediated regulation

Arabidopsis PsbQ, encoding a 16 kDa protein of the oxygen-evolving complex, is regulated by light and is expressed preferentially in leaf tissues. To analyze the components required for light-regulated and organ-specific expression of PsbQA, several promoter constructs were generated and expressed in tobacco. The 2.2 kb promoter could confer organ-specific expression of the reporter gene, whereas regulatory elements for light-dependent induction could not be located within this promoter and the transcribed region extending up to a second exon, represented by a genomic fragment encompassing the gene. The genomic fragment representing the transcribed region, however, could confer light regulation even on a constitutive promoter, as observed by steady-state mRNA analysis in T0 and T1 tobacco plants. The results obtained have led to the conclusion that regulatory elements for organ-specificity mainly reside in the promoter region whereas the transcribed region of the gene has an important role in light regulation.