Abstract
In this review, we report on the recent developments made using both genetics and functional genomics approaches in the discovery of genes controlling root development in rice. QTL detection in classical biparental mapping populations initially enabled the identification of a very large number of large chromosomal segments carrying root genes. Two segments with large effects have been positionally cloned, allowing the identification of two major genes. One of these genes conferred a tolerance to low phosphate content in soil, while the other conferred a tolerance to drought by controlling root gravitropism, resulting in root system expansion deep in the soil. Findings based on the higher-resolution QTL detection offered by the development of association mapping are discussed. In parallel with genetics approaches, efforts have been made to screen mutant libraries for lines presenting alterations in root development, allowing for the identification of several genes that control different steps of root development, such as crown root and lateral root initiation and emergence, meristem patterning, and the control of root growth. Some of these genes are closely phylogenetically related to Arabidopsis genes involved in the control of lateral root initiation. This close relationship stresses the conservation among plant species of an auxin responsive core gene regulatory network involved in the control of post-embryonic root initiation. In addition, we report on several genetic regulatory pathways that have been described only in rice. The complementarities and the expected convergence of the direct and reverse genetic approaches used to decipher the genetic determinants of root development in rice are discussed in regards to the high diversity characterizing this species and to the adaptations of rice root system architecture to different edaphic environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0030-5) contains supplementary material, which is available to authorized users.
Highlights
Roots are essential organs for exploring and exploiting soil resources, such as water and mineral nutrients
Genetic approaches based on the investigation of rice genotypic and phenotypic diversity have allowed the identification of major genes involved in the development of different types of root system architectures, such as DEEPER ROOTING 1 (DRO1) and PHOSPHORUS-STARVATION TOLERANCE 1 (PSTOL1), with functions related to drought tolerance or adaptation to soil with low phosphate content, respectively (Gamuyao et al 2012; Uga et al 2013)
The identification of PSTOL1, which was only possible using a traditional variety, stresses that the effort to explore the diversity of O. sativa that has adapted to a large range of ecosystems must continue
Summary
Roots are essential organs for exploring and exploiting soil resources, such as water and mineral nutrients. A conserved core gene regulatory network regulates post-embryonic root initiation in response to auxin The crown root less 4 (crl4) mutant is impaired in OsGNOM1, which encodes a membrane-associated guaninenucleotide exchange factor for the ADP-ribosylation factor G protein (Kitomi et al 2008; Liu et al 2009).
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