Abstract
This study was aimed at unravelling the molecular basis of root growth behavior in a drought-tolerant upland rice genotype, Nootripathu. Root tips of Nootripathu were found to possess shorter root caps and a greater number of dividing cells, favoring faster elongation compared to shallow-rooted IR20. Width and length of cortical cells in the roots of rapidly growing Nootripathu were found to be two to three times higher than IR20. Evaluation of shallow-rooted IR20, deep-rooted Nootripathu and their Recombinant Inbred Lines (RILs) for root characteristics revealed the presence of genetic variation for root traits among RILs. 2D-PAGE analysis of proteins in roots of IR20, Nootripathu and bulks of extreme RILs differing in root traits resulted in the identification of proteins co-segregating with root growth behavior and co-localized with QTLs for root traits. A putative candidate gene, OsARD4, encoding an “acireductone dioxygenase” was validated for its role in modulating the root growth pattern through genetic transformation. Transgenic ASD16 rice plants engineered for the overexpression of OsARD4 exhibited root growth characteristics similar to those of Nootripathu, including faster radical emergence, more rapid elongation of primary roots, early initiation of crown/lateral roots, and higher root biomass than the non-transgenic plants.
Highlights
Rice (Oryza sativa L.) production has to be raised to approximately 160 million tons by 2050 from the current level of 100 million tons to ensure food security for the increasing global population
This study was aimed at identifying putative candidate genes regulating root growth behavior in the landrace Nootripathu using recent advancements in genomics. 2D-PAGE profiling of proteins was carried out in roots of contrasting rice genotypes, such as IR20, Nootripathu, and bulks of extreme Recombinant Inbred Lines (RILs) exhibiting contrasting root growth characteristics to identify proteins co-segregating with root growth behavior
RILs derived between them exhibited significant genetic variation for primary root length (2.38 cm to 8.83 cm) on 8 DAS (Fig. 1f,g)
Summary
Rice (Oryza sativa L.) production has to be raised to approximately 160 million tons by 2050 from the current level of 100 million tons to ensure food security for the increasing global population. Drought avoidance is vital in maintaining productivity under water-limited environments. It is achieved by maintaining high internal water status through increased absorption of water facilitated by an extensive root system and reduced water loss through the canopy[2]. Root growth-related traits are considered important for sustaining rice productivity under drought and nutrient deficient stresses[4]. (b–d) Mean root number, primary root length and mean root thickness in 45-day old plants of IR20 and Nootripathu. (f) Genetic variation for root growth behavior in 8-day old seedlings of IR20, Nootripathu and their selected RILs (HR,high root; LR, low root). (g) Frequency distribution of primary root length in 8-day old seedlings of IR20, Nootripathu and their RILs. Each data point is the mean of 5 independent measurements. Each data point is the mean of 5 independent measurements. *Indicates significance at P < 0.05, and **Indicates significance at P < 0.01 (one-way ANOVA compared with IR20)
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