Adventitious root formation in rice requires OsGNOM1 and is mediated by the OsPINs family

Abstract

The fibrous root system in cereals comprises primarily adventitious roots (ARs), which play important roles in nutrient and water uptake. Current knowledge regarding the molecular mechanism underlying AR development is still limited. We report here the isolation of four rice (Oryza sativa L.) mutants, from different genetic backgrounds, all of which were defective in AR formation. These mutants exhibited reduced numbers of lateral roots (LRs) and partial loss of gravitropism. The mutants also displayed enhanced sensitivity to N-1-naphthylphthalamic acid, an inhibitor of polar auxin transport (PAT), indicating that the mutations affected auxin transport. Positional cloning using one of the four mutants revealed that it was caused by loss-of-function of a guanine nucleotide exchange factor for ADPribosylation factor (OsGNOM1). RT-PCR and analysis of promoter::GUS transgenic plants showed that OsGNOM1 is expressed in AR primordia, vascular tissues, LRs, root tips, leaves, anthers and lemma veins, with a distribution pattern similar to that of auxin. In addition, the expressions of OsPIN2, OsPIN5b and OsPIN9 were altered in the mutants. Taken together, these findings indicate that OsGNOM1 affects the formation of ARs through regulating PAT.

Root system architecture: insights fromArabidopsisand cereal crops

“…OsGNOM is a guanine nucleotide exchange factor for a GTPase-ADP-ribosylation factor (ARF)-involved in polar auxin transport, and has a high degree of homology to the GNOM protein found in Arabidopsis. Mutants for OsGNOM also have defects in crown root development owing to disrupted distribution of auxin in the shoot tissues at the site of crown root primordia initiation [125].…”

The Interaction between Rice ERF3 and WOX11 Promotes Crown Root Development by Regulating Gene Expression Involved in Cytokinin Signaling

“…During rice root morphogenesis, several developmental stages can be clearly distinguished, including crown root initiation, emergence, and elongation (Itoh et al, 2005;Coudert et al, 2010;Kitomi et al, 2011b;Wang et al, 2011). Although several key genes have been identified and characterized in the regulation of crown root development Liu et al, 2005;Kitomi et al, 2008;Liu et al, 2009;Zhao et al, 2009), the molecular mechanisms of crown root formation and the functional relationship between these genes are not known.…”

“…Arabidopsis lateral root regulatory genes LATERAL ORGAN BOUNDARIES-DOMAIN16/ASYMMETRIC LEAVES2-LIKE18 (LBD16/ASL18) and LBD29/ASL16 are reported to function downstream of AUXIN RESPONSE FACTOR7 (ARF7)-and ARF19-dependent auxin signaling (Okushima et al, 2007;Lee et al, 2009;Goh et al, 2012). In rice, mutants or knockdown transgenic plants of genes involved in auxin signaling pathways and/or polar auxin transport (e.g., CROWN ROOTLESS1 [CRL1]/ADVENTITIOUS ROOTLESS1 [ARL1], CRL4/ GNOM1, CAND1, PIN1, CRL5, Aux/IAA3, and MANNOSYL-OLIGOSACCHARIDE GLUCOSIDASE) display reduced or no crown root phenotypes Liu et al, 2005;Xu et al, 2005;Nakamura et al, 2006;Liu et al, 2009;Kitomi et al, 2011a;Wang et al, 2011;Zhu et al, 2012;Wang et al, 2014). In addition, a gain-of-function mutation of IAA11 affects lateral root development in rice (Nakamura et al, 2006;Zhu et al, 2012).…”

Rice WUSCHEL-related homeobox 3A (OsWOX3A) modulates auxin-transport gene expression in lateral root and root hair development

“…1E and F), suggesting that the altered expression of OsPIN genes in nal2/3 perturbs the precise distribution of endogenous auxin, as previously observed in the rice crown rootless (crl) and pin mutants. 8,[11][12][13] We further tested the effect of exogenous auxin treatment on root hair development in nal2/3. Interestingly, treatment with exogenous auxin further increased root hair growth in nal2/3 mutants (Fig.…”