ABSTRACT
Introduction ................................................................................................................................. 158 Functional genomics tools and techniques ............................................................................. 159
Studying the expression of a genotype ............................................................................... 159 Use of hybridization-based approaches .............................................................................. 160 Next-generation sequencing ................................................................................................. 161
Role of forward and reverse genetics approaches in dening gene function .................... 162 Gene silencing ......................................................................................................................... 163 Posttranscriptional gene silencing (PTGS) ......................................................................... 164 Virus-induced gene silencing ............................................................................................... 164 MicroRNA-induced gene silencing ..................................................................................... 164 Transcriptional gene silencing .............................................................................................. 165 Targeted genome editing ....................................................................................................... 165 Targeting-induced local lesions in genomes ...................................................................... 166
Genome sequencing of plants ................................................................................................... 168 Lessons learnt from genome sequences of model plants ................................................. 168 Overview of the recently sequenced genomes................................................................... 169 Limitations of genome sequencing in plants ..................................................................... 170
Role of functional genomics in crop improvement ................................................................ 173 Gene silencing: A tool for improving resistance to biotic and abiotic stresses in crop plants .......................................................................................................................... 173 Improvement in quality traits .............................................................................................. 174 Improvement in agronomic important traits ..................................................................... 174 Identication of DNA markers ............................................................................................. 174 Translation of information from model to less-studied species ...................................... 174 Discovery of small/regulatory RNAs ................................................................................. 175 Development of new genetic resources .............................................................................. 175
Conclusions .................................................................................................................................. 175 Acknowledgments ...................................................................................................................... 176 References .................................................................................................................................... 176
of these 63% are crop species. The next challenge is to dene the function to these sequences (genes) and their regulation and interaction with the other genes. Though the efforts toward the identication of genes function were started in early 1990s, however, after sequencing of Arabidopsis thaliana (a model plant species), a mega genome project toward the exploration of genes function was initiated. Both the reverse (gene to phenotype) and forward genetics (phenotype to gene) approaches were used. For example, microarray, virus-induced gene silencing, gene knockout, RNA interference, insertional mutagenesis, Targeting Induced Local Lesions IN Genomes, EcoTILLING, next-generation sequencing technologies, etc., have been extensively used for discovering genes and their functions. All these technologies with their own inherent merits and demerits were supplemented by the emerging bioinformatics tools in translating the information generating on model species to a less-studied species-effective tool in predicting function of unknown sequences within the shortest possible time through homology search. All these efforts set a stage for unraveling the functions of unknown genes involved in conferring various mechanisms including growth, grain development, response to various stresses, etc. Thus, the functional genomic studies would lead to sustain crop productivity on this planet by providing a comprehensive knowledge about the function of genes-a huge genetic resource that can be utilized for improving crop varieties using nonconventional (genetic transformation) and conventional means assisted with DNA markers.
