Response and transcriptional regulation of rice SUMOylation system during development and stress conditions

Modification of proteins by the reversible covalent addition of the small ubiquitin like modifier (SUMO) protein has important consequences affecting target protein stability, sub-cellular localization, and protein-protein interactions. SUMOylation involves a cascade of enzymatic reactions, which resembles the process of ubiquitination. In this study, we characterized the SUMOylation system from an important crop plant, rice, and show that it responds to cold, salt and ABA stress conditions on a protein level via the accumulation of SUMOylated proteins. We also characterized the transcriptional regulation of individual SUMOylation cascade components during stress and development. During stress conditions, majority of the SUMO cascade components are transcriptionally down regulated. SUMO conjugate proteins and SUMO cascade component transcripts accumulated differentially in various tissues during plant development with highest levels in reproductive tissues. Taken together, these data suggest a role for SUMOylation in rice development and stress responses

Characterization of cold shock domain proteins and SUMOylation system from Oryza sativa

In the first part of this study, two novel c&barbelow;old s&barbelow;hock domain p&barbelow;roteins from rice (OsCSP) were cloned and subsequently characterized their roles during stress conditions and development. OsCSP1 and OsCSP2 ( Oryza sativa CSD protein) encode putative proteins consisting of an N-terminal CSD and glycine-rich regions that are interspersed by 4 and 2 CX2CX4HX4C (CCHC) retroviral-like zinc fingers, respectively. Using an in vitro DNA binding assay, I demonstrate that OsCSPs exhibit conserved ssDNA binding activity. In vivo functional complementation in a cold-sensitive bacterial strain, that lacks four cold inducible cold shock domain proteins revealed that OsCSPs function as RNA chaperones, similar to their bacterial and winter wheat counterparts. To understand the functions of these genes in rice, I studied the transcriptional regulation in response to abiotic stress conditions. Under cold stress, OsCSP transcript levels are only transiently and marginally increased and the encoded proteins did not accumulate. These transcript and protein data are in sharp contrast with the observed data for winter wheat and Arabidopsis cold shock domain proteins under cold stress. In these species, both transcripts and protein levels of CSPs are increased upon cold stress. Based on these data, it can be hypothesized that the accumulation of cold shock domain proteins may play an important role in determining the cold acclimation capability of the plants. Expression analysis at the protein and RNA levels during development revealed that OsCSPs are highly expressed in the reproductive and meristematic tissues. These results indicate a potential role for rice cold shock domain proteins in plant growth and reproductive development.;In this study, I also characterized the post-translational modification of plant cold shock domain proteins by SUMOylation. Post-translational modifications can impart rapid changes in protein function. SUMOylation involves the reversible attachment of a small protein called SUMO (small ubiquitin-like modifier) to target proteins. The SUMO protein has a similar three dimensional structure as that of ubiquitin and the process of SUMOylation is very similar to that of ubiquitination. However, unlike ubiquitination, SUMOylation is not implicated in protein degradation. SUMO modification can affect the target protein stability, sub-cellular localization protein-protein interactions. Using a computational approach on rice and Arabidopsis cold shock domain proteins, I identified canonical SUMOylation motifs in both rice CSPs and one of the Arabidopsis CSPs. Using in vitro assays, I demonstrated that both OsCSPs can undergo SUMOylation. Using mutational approaches, I identified an important lysine residue for SUMOylation in Arabidopsis AtCSP1. By employing GFP-tagged wild-type and variant AtCSP1 proteins, I demonstrate that SUMOylation appears to affect AtCSP1 protein localization.;In another study, I characterized the entire SUMO conjugation system in rice. The process of SUMOylation involves a cascade of enzymatic reactions involving activation (E1) enzymes, conjugation (E2) enzymes and ligation (E3) enzymes. I compared the protein sequences of all these genes from rice with those from Arabidopsis, yeast and human. This revealed a high amino acid sequence conservation of individual SUMOylation components from yeast to plants and animals. In Arabidopsis, the SUMOylation system has been implicated in plant development and in mediating abiotic stress responses. To understand the role of the rice SUMOylation system during development, I studied the SUMO conjugate profiles and the expression of individual SUMO component genes in various tissues at different stages of plant development. The highest levels of SUMOylated proteins were observed in panicles and meristematic tissues. Expression studies revealed that SUMO component genes are highly expressed in reproductive tissues like developing seeds and panicles. Together, these data implicate an important role for the rice SUMOylation system in plant growth and reproductive development. To understand the role of SUMOylation system in rice, I studied SUMO conjugate profiles and the transcriptional regulation of individual SUMO components during cold, salt and ABA stress conditions. Rice responds to these stresses by accumulating SUMO conjugated proteins, suggesting that protein SUMOylation helps to mediate plant stress responses. Studies on the transcriptional regulation of individual SUMO pathway genes during these stress conditions revealed that most are transcriptionally down-regulated. However, a particular SUMO E3 ligase gene (OsSIZ2) is transiently up-regulated upon exposure to all three stress conditions. Considering the importance of E3 ligases in improving the efficiency and specificity of the SUMO conjugation reactions, OsSIZ2 may mediate accumulation of SUMO conjugates during these stress conditions. Taken together, these data suggest a role for SUMOylation in rice development and stress responses. (Abstract shortened by UMI.)

Marker-Assisted Breeding of Improved Maternal Haploid Inducers in Maize for the Tropical/Subtropical Regions

For efficient production of doubled haploid (DH) lines in maize, maternal haploid inducer lines with high haploid induction rate (HIR) and good adaptation to the target environments is an important requirement. In this study, we present second-generation Tropically Adapted Inducer Lines (2GTAILs), developed using marker assisted selection (MAS) for qhir1, a QTL with a significant positive effect on HIR from the crosses between elite tropical maize inbreds and first generation Tropically Adapted Inducers Lines (TAILs). Evaluation of 2GTAILs for HIR and agronomic performance in the tropical and subtropical environments indicated superior performance of 2GTAILs over the TAILs for both HIR and agronomic performance, including plant vigor, delayed flowering, grain yield, and resistance to ear rots. One of the new inducers 2GTAIL006 showed an average HIR of 13.1% which is 48.9% higher than the average HIR of the TAILs. Several other 2GTAILs also showed higher HIR compared to the TAILs. While employing MAS for qhir1 QTL, we observed significant influence of the non-inducer parent on the positive effect of qhir1 QTL on HIR. The non-inducer parents that resulted in highest mean HIR in the early generation qhir1+ families also gave rise to highest numbers of candidate inducers, some of which showed transgressive segregation for HIR. The mean HIR of early generation qhir1+ families involving different non-inducer parents can potentially indicate recipient non-inducer parents that can result in progenies with high HIR. Our study also indicated that the HIR associated traits (endosperm abortion rate, embryo abortion rate, and proportion of haploid plants among the inducer plants) can be used to differentiate inducers vs. non-inducers but are not suitable for differentiating inducers with varying levels of haploid induction rates. We propose here an efficient methodology for developing haploid inducer lines combining MAS for qhir1 with HIR associated traits

Relationship between grain yield and quality traits under optimum and low-nitrogen stress environments in tropical maize

Breeding for nitrogen use efficiency (NUE) is important to deal with food insecurity and its effect on grain quality, particularly protein. A total of 1679 hybrids were evaluated in 16 different trials for grain yield (GY), grain quality traits (protein, starch and oil content) and kernel weight (KW) under optimum and managed low soil nitrogen fields in Kiboko, Kenya, from 2011 to 2014. The objectives of our study were to understand (i) the effect of low soil N stress on GY and quality traits, (ii) the relationship between GY and quality traits under each soil management condition and (iii) the relationship of traits with low-N versus optimum conditions. From the results, we observed the negative effects of low N on GY, KW and the percentage of protein content, and a positive effect on the percentage of starch content. The correlation between GY and all quality traits was very weak under both soil N conditions. GY had a strong relationship with KW under both optimum and low soil N conditions. Protein and starch content was significantly negative under both optimum and low-N conditions. There was no clear relationship among quality traits under optimum and low N, except for oil content. Therefore, it seems feasible to simultaneously improve GY along with quality traits under both optimum and low-N conditions, except for oil content. However, the negative trend observed between GY (starch) and protein content suggests the need for the regular monitoring of protein and starch content to identify varieties that combine both high GY and acceptable quality. Finally, we recommend further research with a few tropical maize genotypes contrasting for NUE to understand the relationship between the change in grain quality and NUE under low-N conditions

Bioactive compounds and antibacterial activities in crystallized honey liquefied with ultrasound

The effect of ultrasound on the crystal size, phenols, flavonoids, Maillard products and antibacterial activity of crystallized honeys was studied. Three multifloral honeys (M), one monofloral (MO) and one honeydew (HD) honey were used. Ultrasound was performed at 42 kHz for different times (0, 5, 10 and 15 min). The antibacterial activities were tested against Salmonella typhimurium, Bacillus subtilis, Pseudomonas aeruginosa, Listeria mono cytogenes, Staphylococcus aureus and Escherichia coli. In all honeys, the parameters analyzed had significant dif ferences ((P < 0.05)). After 15 min of ultrasound the HD had increments of 44 mg of gallic acid/100 g of honey in phenols, and some M showed increase in flavonoids (5.64 mg of quercitin /100 g of honey) and improvement in inhibition against Salmonella typhimurium was 13.1%. In some honeys the correlation between phenols or fla vonoids and antibacterial activity were significant ((P < 0.05)). No correlation was found between Maillard products and antibacterial activity. The ultrasound treatment effect on the crystal size, phenols, flavonoid, Maillard products, and antibacterial activity of crystallized honeys were different in each honey.info:eu-repo/semantics/publishedVersio

A diallel analysis of a maize donor population response to In vivo maternal haploid induction II: haploid male fertility

Doubled haploid (DH) lines are used in maize breeding to accelerate the breeding cycle and create homogenous inbred lines in as little as two seasons. These pure inbred lines allow breeders to quickly evaluate new cross combinations. There are two important steps in creating DH lines: 1) generation and selection of haploid progeny, and 2) genome doubling to create fertile, diploid inbreds. Colchicine is widely used to artificially double genomes in haploid plants, which is hazardous, expensive, and time consuming. In this study, three public inbred lines A427, A637, and NK778 were found to have substantial haploid male fertility (HMF). A six-parent full diallel between these three HMF lines and three non-HMF lines was created and HMF was scored. Diallel analysis revealed significant GCA estimates of up to 17% for HMF, as well as significant SCA effects of up to 25%. No significant reciprocal effects were found. HMF is promising to be incorporated into elite maize breeding programs to potentially overcome the need of using colchicine treatments for genome doubling. Colchicine aided doubling success rates varying from almost zero to 30%. HMF has an advantage over artificial genome doubling both in terms of increased success rates and decreased costs for DH line production

Genomic-based-breeding tools for tropical maize improvement

Maize has traditionally been the main staple diet in the Southern Asia and Sub-Saharan Africa and widely grown by millions of resource poor small scale farmers. Approximately, 35.4 million hectares are sown to tropical maize, constituting around 59% of the developing worlds. Tropical maize encounters tremendous challenges besides poor agro-climatic situations with average yields recorded <3 tones/hectare that is far less than the average of developed countries. On the contrary to poor yields, the demand for maize as food, feed, and fuel is continuously increasing in these regions. Heterosis breeding introduced in early 90 s improved maize yields significantly, but genetic gains is still a mirage, particularly for crop growing under marginal environments. Application of molecular markers has accelerated the pace of maize breeding to some extent. The availability of array of sequencing and genotyping technologies offers unrivalled service to improve precision in maize-breeding programs through modern approaches such as genomic selection, genome-wide association studies, bulk segregant analysis-based sequencing approaches, etc. Superior alleles underlying complex traits can easily be identified and introgressed efficiently using these sequence-based approaches. Integration of genomic tools and techniques with advanced genetic resources such as nested association mapping and backcross nested association mapping could certainly address the genetic issues in maize improvement programs in developing countries. Huge diversity in tropical maize and its inherent capacity for doubled haploid technology offers advantage to apply the next generation genomic tools for accelerating production in marginal environments of tropical and subtropical world. Precision in phenotyping is the key for success of any molecular-breeding approach. This article reviews genomic technologies and their application to improve agronomic traits in tropical maize breeding has been reviewed in detail