Abstract
The huge variation in root system architecture (RSA) among different rice (Oryza sativa) cultivars is conferred by their genetic makeup and different growth or climatic conditions. Unlike model plant Arabidopsis, the molecular basis of such variation in RSA is very poorly understood in rice. Cultivars with stable variation are valuable resources for identification of genes involved in RSA and related physiological traits. We have screened for RSA and identified two such indica rice cultivars, IR-64 (OsAS83) and IET-16348 (OsAS84), with stable contrasting RSA. OsAS84 produces robust RSA with more crown roots, lateral roots and root hairs than OsAS83. Using comparative root transcriptome analysis of these cultivars, we identified genes related to root development and different physiological responses like abiotic stress responses, hormone signaling, and nutrient acquisition or transport. The two cultivars differ in their response to salinity/dehydration stresses, phosphate/nitrogen deficiency, and different phytohormones. Differential expression of genes involved in salinity or dehydration response, nitrogen (N) transport, phosphate (Pi) starvation signaling, hormone signaling and root development underlies more resistance of OsAS84 towards abiotic stresses, Pi or N deficiency and its robust RSA. Thus our study uncovers gene-network involved in root development and abiotic stress responses in rice.
Highlights
CR emergence, OsWOX3A regulates LR development and RH formation, and OsSCR1 and OsSCR2 are involved in regulation of asymmetric division of cortex/endodermis progenitor cells and initiation of root development[9,10,11]
Auxin and AUX/IAA (AUXIN/INDOLE ACETIC ACID) proteins regulate the expression of CROWN ROOTLESS1 (CRL1), which encodes for Arabidopsis homologs LBD16/LBD19, which are ASYMMETRIC LEAVES (AS2)/LATERAL ORGAN BOUNDARIES (LOB) family transcription factor13. crl[1] mutant showed defects in CR formation and alteration in other auxin-related root system architecture (RSA) traits such as reduced LR number, auxin insensitivity in LR formation and impaired root gravitropism[13]
The CRL1 promoter contains an auxin responsive element (ARE), which binds with the OsARF16, a ortholog of ARF7 and ARF19 of Arabidopsis[14]
Summary
CR emergence, OsWOX3A regulates LR development and RH formation, and OsSCR1 and OsSCR2 are involved in regulation of asymmetric division of cortex/endodermis progenitor cells and initiation of root development[9,10,11]. Our results indicate that differential expression of various transporters, transcription factors and genes involved in hormonal signaling could largely contribute to the phenotypic and physiological differences observed between two cultivars.
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