Distinct domains of the AVRPM3A2/F2 avirulence protein from wheat powdery mildew are involved in immune receptor recognition and putative effector function.

Recognition of the AVRPM3A2/F2 avirulence protein from powdery mildew by the wheat PM3A/F immune receptor induces a hypersensitive response after co-expression in Nicotiana benthamiana. The molecular determinants of this interaction and how they shape natural AvrPm3a2/f2 allelic diversity are unknown. We sequenced the AvrPm3a2/f2 gene in a worldwide collection of 272 mildew isolates. Using the natural polymorphisms of AvrPm3a2/f2 as well as sequence information from related gene family members, we tested 85 single-residue-altered AVRPM3A2/F2 variants with PM3A, PM3F and PM3FL456P/Y458H (modified for improved signaling) in Nicotiana benthamiana for effects on recognition. An intact AvrPm3a2/f2 gene was found in all analyzed isolates and the protein variant recognized by PM3A/F occurred globally at high frequencies. Single-residue alterations in AVRPM3A2/F2 mostly disrupted, but occasionally enhanced, the recognition response by PM3A, PM3F and PM3FL456P/Y458H . Residues enhancing hypersensitive responses constituted a protein domain separate from both naturally occurring polymorphisms and positively selected residues of the gene family. These results demonstrate the utility of using gene family sequence diversity to screen residues for their role in recognition. This approach identified a putative interaction surface in AVRPM3A2/F2 not polymorphic in natural alleles. We conclude that molecular mechanisms besides recognition drive AvrPm3a2/f2 diversification.

Enhancing C3 photosynthesis: an outlook on feasible interventions for crop improvement.

Despite the declarations and collective measures taken to eradicate hunger at World Food Summits, food security remains one of the biggest issues that we are faced with. The current scenario could worsen due to the alarming increase in world population, further compounded by adverse climatic conditions, such as increase in atmospheric temperature, unforeseen droughts and decreasing soil moisture, which will decrease crop yield even further. Furthermore, the projected increase in yields of C3 crops as a result of increasing atmospheric CO2 concentrations is much less than anticipated. Thus, there is an urgent need to increase crop productivity beyond existing yield potentials to address the challenge of food security. One of the domains of plant biology that promises hope in overcoming this problem is study of C3 photosynthesis. In this review, we have examined the potential bottlenecks of C3 photosynthesis and the strategies undertaken to overcome them. The targets considered for possible intervention include RuBisCO, RuBisCO activase, Calvin-Benson-Bassham cycle enzymes, CO2 and carbohydrate transport, and light reactions among many others. In addition, other areas which promise scope for improvement of C3 photosynthesis, such as mining natural genetic variations, mathematical modelling for identifying new targets, installing efficient carbon fixation and carbon concentrating mechanisms have been touched upon. Briefly, this review intends to shed light on the recent advances in enhancing C3 photosynthesis for crop improvement.

Phloem-specific expression of the lectin gene from Allium sativum confers resistance to the sap-sucker Nilaparvata lugens.

Rice production is severely hampered by insect pests. Garlic lectin gene (ASAL) holds great promise in conferring protection against chewing (lepidopteran) and sap-sucking (homopteran) insect pests. We have developed transgenic rice lines resistant to sap-sucking brown hopper (Nilaparvata lugens) by ectopic expression of ASAL in their phloem tissues. Molecular analyses of T0 lines confirmed stable integration of transgene. T1 lines (NP 1-2, 4-3, 11-6 & 17-7) showed active transcription and translation of ASAL transgene. ELISA revealed ASAL expression was as high as 0.95% of total soluble protein. Insect bioassays on T2 homozygous lines (NP 18 & 32) revealed significant reduction (~74-83%) in survival rate, development and fecundity of brown hoppers in comparison to wild type. Transgenics exhibited enhanced resistance (1-2 score) against brown hoppers, minimal plant damage and no growth penalty or phenotypic abnormalities.

Multi-Omics Pipeline and Omics-Integration Approach to Decipher Plant's Abiotic Stress Tolerance Responses.

The present day's ongoing global warming and climate change adversely affect plants through imposing environmental (abiotic) stresses and disease pressure. The major abiotic factors such as drought, heat, cold, salinity, etc., hamper a plant's innate growth and development, resulting in reduced yield and quality, with the possibility of undesired traits. In the 21st century, the advent of high-throughput sequencing tools, state-of-the-art biotechnological techniques and bioinformatic analyzing pipelines led to the easy characterization of plant traits for abiotic stress response and tolerance mechanisms by applying the 'omics' toolbox. Panomics pipeline including genomics, transcriptomics, proteomics, metabolomics, epigenomics, proteogenomics, interactomics, ionomics, phenomics, etc., have become very handy nowadays. This is important to produce climate-smart future crops with a proper understanding of the molecular mechanisms of abiotic stress responses by the plant's genes, transcripts, proteins, epigenome, cellular metabolic circuits and resultant phenotype. Instead of mono-omics, two or more (hence 'multi-omics') integrated-omics approaches can decipher the plant's abiotic stress tolerance response very well. Multi-omics-characterized plants can be used as potent genetic resources to incorporate into the future breeding program. For the practical utility of crop improvement, multi-omics approaches for particular abiotic stress tolerance can be combined with genome-assisted breeding (GAB) by being pyramided with improved crop yield, food quality and associated agronomic traits and can open a new era of omics-assisted breeding. Thus, multi-omics pipelines together are able to decipher molecular processes, biomarkers, targets for genetic engineering, regulatory networks and precision agriculture solutions for a crop's variable abiotic stress tolerance to ensure food security under changing environmental circumstances.

Cloning and molecular characterization of a gene encoding late embryogenesis abundant protein from Pennisetum glaucum: protection against abiotic stresses.

Late embryogenesis abundant (LEA) protein family is a large protein family that protects other proteins from aggregation due to desiccation or osmotic stresses. A cDNA clone encoding a group 7 late embryogenesis abundant protein, termed PgLEA, was isolated from Pennisetum glaucum by screening a heat stress cDNA library. PgLEA cDNA encodes a 176 amino acid polypeptide with a predicted molecular mass of 19.21 kDa and an estimated isoelectric point of 7.77. PgLEA shares 70-74% sequence identity with other plant homologs. Phylogenetic analysis revealed that PgLEA is evolutionarily close to the LEA 7 group. Recombinant PgLEA protein expressed in Escherichia coli possessed in vitro chaperone activity and protected PgLEA-producing bacteria from damage caused by heat and salinity. Positive correlation existed between differentially up-regulated PgLEA transcript levels and the duration and intensity of different environmental stresses. In silico analysis of the promoter sequence of PgLEA revealed the presence of a distinct set of cis-elements and transcription factor binding sites. Transcript induction data, the presence of several putative stress-responsive transcription factor binding sites in the promoter region of PgLEA, the in vitro chaperone activity of this protein and its protective effect against heat and salt damage in E. coli suggest a role in conferring abiotic stress tolerance in plants.

Molecular and structural analysis of C4-specific PEPC isoform from Pennisetum glaucum plays a role in stress adaptation.

Phosphoenolpyruvate carboxylase is an ubiquitous cytosolic enzyme that catalyzes the ß-carboxylation of phosphoenolpyruvate (PEP) and is encoded by multigene family in plants. It plays an important role in carbon economy of plants by assimilating CO2 into organic acids for subsequent C4 or CAM photosynthesis or to perform several anaplerotic roles in non-photosynthetic tissues. In this study, a cDNA clone encoding for PEPC polypeptide possessing signature motifs characteristic to ZmC4PEPC was isolated from Pennisetum glaucum (PgPEPC). Deduced amino acid sequence revealed its predicted secondary structure consisting of forty alpha helices and eight beta strands is well conserved among other PEPC homologs irrespective of variation in their primary amino acid sequences. Predicted PgPEPC quartenary structure is a tetramer consisting of a dimer of dimers,which is globally akin to maize PEPC crystal structure with respect to major chain folding wherein catalytically important amino acid residues of active site geometry are conserved. Recombinant PgPEPC protein expressed in E. coli and purified to homogeneity, possessed in vitro ß-carboxylation activity that is determined using a coupled reaction converting PEP into malate. Tetramer is the most active form, however, it exists in various oligomeric forms depending upon the protein concentration, pH, ionic strength of the media and presence of its substrate or effecters. Recombinant PgPEPC protein confers enhanced growth advantage to E. coli under harsh growth conditions in comparison to their respective controls; suggesting that PgPEPC plays a significant role in stress adaptation.