Agrobacterium-mediated genetic transformation of commercially elite rice restorer line using nptII gene as a plant selection marker

Optimisation of a rapid and efficient transformation protocol for fungal blast-susceptible indica rice cultivars HR-12 and CO-39

Rice is an important staple crop and fungal blast disease destroys about 10-30% of its global produce, annually. Although genetic manipulation has largely been employed in crop-improvement programmes and agricultural biotechnology, the ease of transformation of several recalcitrant indica cultivars continues to be a challenge. HR-12 and CO-39 are two indica cultivars that are commonly used in breeding programmes, but are susceptible to biotic threats like fungal blast and sheath blight disease. Here in this study, we have optimised a rapid and reproducible transformation protocol for the said cultivars, having compared both the tissue-culture and in-planta methods of transformation. Murashige & Skoog basal media supplemented with maltose and 2.5 mg l^-1 2,4-D induced efficient callogenesis in HR-12, while maltose with 3 mg l^-1 2,4-D gave optimum results in case of CO-39. The media containing 0.5 mg l^-1 NAA, 3 mg l^-1 BAP, and 1 mg l^-1 kinetin yielded a maximum regeneration efficiency of 62% and 65% in HR-12 and CO-39, respectively. The studies with Agrobacterium tumefaciens, LBA4404 strain harbouring pCAMBIA1303 suggested that although these cultivars demonstrated successful gene-transfer, they failed to regenerate efficiently, post-transformation. Alternatively, our modified in-planta piercing and vacuum infiltration-based protocol resulted in 33-35% transformation efficiency in less than half the time required for tissue-culture based transformation method. As per our knowledge, it is among the highest obtained from existing piercing-based direct transformation protocols in rice, and can also be implemented in genetically manipulating other recalcitrant varieties of rice.

Establishment of Agrobacterium rhizogenes-mediated hairy root transformation of Crocus sativus L

Efficient transformation system for genetic improvement is essential in Crocus sativus, as it lacks sexual reproduction. This is the first report wherein an efficient protocol is developed for the transformation of Crocus sativus L. by Agrobacterium rhizogenes strain ARqua1 with a transformation efficiency of 78.51%. The ARqua1 strain harboring both Ri plasmid and binary vector plasmid pSITE-4NB, and marker genes for red fluorescent protein (RFP) and a β-glucuronidase (GUS) reporter gene were used for selection. Transformation was confirmed by RFP signal, GUS reporter assay and polymerase chain reaction (PCR) analysis of the test samples after 21 days post inoculation. These results confirm the establishment of protocol for hairy root transformation in C. sativus that can be further used for gene transfer or gene editing in Crocus for its genetic improvement.

A Versatile Vector Toolkit for Functional Analysis of Rice Genes

BACKGROUND

Rice (Oryza sativa) is the main food for half of the world's population, and is considered the model for molecular biology studies of monocotyledon species. Although the rice genome was completely sequenced about 15 years ago, the function of most rice genes is still unknown.

RESULTS

In this study, we developed a vector toolkit that contains 42 vectors for transient expression studies in rice protoplasts and stable expression analysis in transgenic rice. These vectors have been successfully used to study protein subcellular localization, protein-protein interaction, gene overexpression, and the CRISPR/Cas9-mediated gene editing. A novel feature of these vectors is that they contain a universal multiple cloning site, which enables more than 99% of the rice coding sequences to be conveniently transferred between vectors.

CONCLUSIONS

The versatile vectors represent a highly efficient and high-throughput toolkit for functional analysis of rice genes.