Os06g0597000

OsIAA23, an Aux/IAA gene in rice, which stabilizing mutation exhibited defects in postembryonic maintenance of the quiescent center (QC) that caused the disintegration of the root cap and termination of root growth.

Annotated Information

Function

This gene, OsIAA23, is a mutation of Aux/IAA gene in rice. The mutant is characterized by a loss of QC identity during postembryonic development, and the displayed defects result from a stabilizing mutation in domain II of OsIAA23 (Os06g39590). (1)Characterization of the mutant is show in Figure 1.

Figure 1. Characterization of the mutant. (a) Root growth of 5-day-old seedlings of the wild type (WT) (left) and the heterozygous (middle) and homozygous mutant (right). Bar = 2 cm. (b–d) Cross-sections at the stem base of the WT (b), heterozygous mutant (c), and homozygous mutant (d). Bar = 0.5 mm. (e) Plants at the grain filling stage. From left to right: WT, the heterozygous mutant, and the homozygous mutant. (f) The panicle of three genotypes. From left to right: WT, the heterozygous mutant, and the homozygous mutant. Bar = 2 cm. (g–i) Stereomicroscopic images of OsCYCB1;1p::GUS in the roots of the three genotypes. From left to right: WT, the heterozygous mutant, and the homozygous mutant. Bar = 0.5 mm. (j) Gravitropic response of three genotypes. Seedlings were grown for 5 days under g1 gravitropic conditions and then moved to g2 where they were grown for 2 additional days. From top to bottom: WT, the heterozygous mutant, and the homozygous mutant. Bar = 2 cm.

(2) Cloning of the OsIAA23 gene Heterozygous Osiaa23 (japonica) was crossed with Kasalath (indica). Approximately half of the F1 population that exhibited the heterozygous mutant phenotype was selected and self-pollinated. The derived F2 population was used to map OsIAA23. The OsIAA23 gene, sequenced from homozygous mutant genomic DNA, was found to contain a G to A base pair substitution causing a glycine (G) to glutamate (E) change (Gly64Glu) in domain II of OsIAA23 (Figure 2). These results confirm that the root tissue defects in the mutant are caused by the point mutation in domain II of OsIAA23.

Figure 2. Map-based cloning and complementation test of OsIAA23. (a) A point mutation was detected in the mutant, which resulted in a G to A base pair change of an Aux/IAA gene (OsIAA23), causing a change of glycine (G) to glutamate (E) in the conserved core sequence of domain II. The exons of OsIAA23 are indicated by thick rectangles, and introns are indicated by thin lines. The four domain positions are indicated by black boxes. (b) Confirmation of the point mutation in OsIAA23 using the dCAPS marker. From left to right: the WT, the heterozygous OsIAA23, and the homozygous OsIAA23, respectively. (c) Two transgenic plants containing the OsIAA23 gene exhibited phenotypes characteristic of the heterozygous and homozygous OsIAA23.

(3) Response to auxin is reduced in Osiaa23 To investigate the auxin response of the Osiaa23 mutant,WT and Osiaa23 mutants were treated with a-naphthalene acetic acid (NAA). These results indicated a reduced sensitivity to auxin in the Osiaa23 mutant (Figure 3).

Figure 3. Alteration of auxin response in the Osiaa23 mutant. (a) Root growth performance of the wild type (WT; left) and Osiaa23 (right) plants grown in a solution culture with 1 lM NAA for 7 days. Bar = 1 cm. (b) Proliferation of root hairs at the root apex of WT (left) and Osiaa23 (right) induced by 0.1 lM NAA treatment. Bar = 0.5 mm. (c, d) Cross-sections indicate DR5p::GUS expression in the root zone with the initiation of lateral root (LR) primordia of WT (c) and Osiaa23 (d). Bars = 20 lm. (e, f) GUS staining of cross-sections at the shoot base with the initiation of crown root primordial in WT (e) and Osiaa23 (f). Bar = 0.5 mm. (g, h) GUS staining of the root apex of 1 d-old seedlings of WT and Osiaa23. Bars = 100 lm.

(4) Reduction of auxin signaling mediated by OsIAA23 is important for crown root primordia development. (5) OsIAA23 does not act only in the QC, but auxin signaling mediated by OsIAA23 in the QC plays a unique role in QC maintenance.

Expression

OsIAA23 was found to be constitutively expressed in all of the examined tissues, although a lower abundance was observed in the embryo (Figure 4).

Figure 4. Expression pattern of OsIAA23 revealed by a GUS reporter line (a, b) Stereomicroscope images showing GUS staining in the primary root tip (a) and the lateral root (LR) (b). Bar = 200 lm. (c) Vertical section of the root tip of the transgenic plants. (d, e) Cross section at the matured root zone with the initiation of LR primordia of the transgenic plants and the magnified view of the stele (e). Bar = 20 lm. (f, g) OsIAA23 (f) and QHB (g) expression during the process of LR primordia development. Bar = 20 lm. (h–j) Cross-sections at the shoot base. (h), (i) and (j) are different stages of crown root primordia. Bar = 100 lm.

Evolution

Aux/IAA and auxin response factor (ARF) are two important families that have been well recognized for their roles in auxin-mediated responses. Aux/IAA proteins are short-lived transcriptional regulators that mediate the auxin responses through interaction with ARF transcription factors.There are 31 members of Aux/IAA family genes in rice(OsIAA1- OsIAA31). The first rice Aux/IAA gene (LOC_Os03g53150) was reported by Thakur et aland they demonstrated that the Aux/IAA gene appears to have same function as the homology genes in Arabidopsis(Figure 5)'（Figure 6）'.

Figure 5. Phylogenetic relationship among the rice gene Aux/IAA Phylogenetic relationship among the rice gene Aux/IAA Proteins The unrooted tree was generated using ClustalX program by neighbor-joining method. Bootstrap values (above 50%) from 1,000 replicates are indicated at each node. Two rice ARF protein sequences (OsARF1, AJ306306 and OsARF2, AB071293) were used as outgroup. b Exon–intron organization of corresponding Aux/ IAA genes. The exons and introns are represented by black boxes and lines, respectively. The numbers 0, 1, and 2 represent phase 0, 1, and 2 introns, respectively

Figure 6. Real-time PCR expression profiles of individual OsIAA genes. The relative mRNA levels of individual OsIAA genes normalized with respect to housekeeping gene, UBQ5, in different tissues (ES etiolated shoots, GS green shoots, R roots, F flowers, C callus). b The relative mRNA levels of individual OsIAA genes in control (16 h auxin depleted) and 2,4-D (30 μm) treated coleoptile segments of 3-day-old etiolated rice seedlings. Asterisks indicate that the expression was close to the detection limit. OsIAA28 could not be amplified at all, whereas OsIAA29 transcription was detected only in roots and that too at very low level. The range of differences between the duplicates was 8–25%.

Labs working on this gene

1. State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China;

2. National Center of Plant Gene Research (Wuhan), National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China;

3. Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India.

References

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Structured Information

Gene Name	Os06g0597000
Description	Similar to Auxin responsive protein IAA-Re
Version	NM_001064521.1 GI:115468773 GeneID:4341432
Length	1519 bp
Definition	Oryza sativa Japonica Group Os06g0597000, complete gene.
Source	Oryza sativa Japonica Group ORGANISM Oryza sativa Japonica Group Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta; Spermatophyta; Magnoliophyta; Liliopsida; Poales; Poaceae; BEP clade; Ehrhartoideae; Oryzeae; Oryza.
Chromosome	Chromosome 6
Location	Chromosome 6:24378976..24380494
Sequence Coding Region	24379095..24379270,24379356..24379676,24379766..24379827,24379946..24379968
Expression	GEO Profiles:Os06g0597000
Genome Context	<gbrowseImage1> name=NC_008399:24378976..24380494 source=RiceChromosome06 preset=GeneLocation </gbrowseImage1>
Gene Structure	<gbrowseImage2> name=NC_008399:24378976..24380494 source=RiceChromosome06 preset=GeneLocation </gbrowseImage2>
Coding Sequence	<cdnaseq>atgtcgacgagctccggcgccgactcgtccccgcccgtctcgggcctcgactacgacgacaccgccctcaccctcgccctccccggctcctcctcctcctcctcctccaccgccgaccccgaacgcaagcgcgccgcccacgccgaccacgccgacgccaagccgccttccccaaaggcgcgggcggtggggtggccgccggtgagggcgtacaggcggaacgcgctgcgggaggactccgcgagggcgaagctggtcaaggtggccgtggacggcgcgccgtacctgcgcaaggtggacctcgcggcgcacgccggctacgcgcccctcctccgcgcgctccacggcatgttcgcctcctgcctcgccgtccgcggcggcggcggcggcgacggcgagggtacaaagctcgtcgacttggtcaccggcgccgagtacgtgcccacctacgaggacaaggacggcgactggatgctcgtcggcgacgtcccctggaagatgttcgtcgagtcctgcaagcggatccgtctcatgaagagctccgaggccgtcaacttatcgccaagacgatcatccagataa</cdnaseq>
Protein Sequence	<aaseq>MSTSSGADSSPPVSGLDYDDTALTLALPGSSSSSSSTADPERKR AAHADHADAKPPSPKARAVGWPPVRAYRRNALREDSARAKLVKVAVDGAPYLRKVDLA AHAGYAPLLRALHGMFASCLAVRGGGGGDGEGTKLVDLVTGAEYVPTYEDKDGDWMLV GDVPWKMFVESCKRIRLMKSSEAVNLSPRRSSR</aaseq>
Gene Sequence	<dnaseqindica>120..295#381..701#791..852#971..993#accaccacacccctcgtctccgcaaactcgacgcgccactcgacagcgaccccgcagccgatccatcccgccgccgaagcagcagcaaccgccacggtgcgccgccgccgccggtaccgatgtcgacgagctccggcgccgactcgtccccgcccgtctcgggcctcgactacgacgacaccgccctcaccctcgccctccccggctcctcctcctcctcctcctccaccgccgaccccgaacgcaagcgcgccgcccacgccgaccacgccgacgccaagccgccttccccaaagtacgtatagcttatgctctctttatggagattcctacgttcccgcgggtttctgacctggcgatcgatcgatgcgtgtgcgcagggcgcgggcggtggggtggccgccggtgagggcgtacaggcggaacgcgctgcgggaggactccgcgagggcgaagctggtcaaggtggccgtggacggcgcgccgtacctgcgcaaggtggacctcgcggcgcacgccggctacgcgcccctcctccgcgcgctccacggcatgttcgcctcctgcctcgccgtccgcggcggcggcggcggcgacggcgagggtacaaagctcgtcgacttggtcaccggcgccgagtacgtgcccacctacgaggacaaggacggcgactggatgctcgtcggcgacgtcccctggaagtaagcaacgcgtgtacacatctcaatcagttcttgccgattaattcaccgaaatcaaatgcaaaatctgatccgatcaatcaacacaggatgttcgtcgagtcctgcaagcggatccgtctcatgaagagctccgaggccgtcaacttatgtaagaacttgcgatccaatccactataataatccaataacattacattaccaactatactaattactgcaacgatcgatgagtgaatgacatttcgattctgaattttttgatgcagcgccaagacgatcatccagataatcgatcctaccacacgcaacgatgcaatgccgcaattgatctgtctgtctgtctgtctgtctgaattagttcgtctgaaagtgtgtgcaatggaagaggcttggctgtacaggtcctccatgcatatgtacctataccgtagtaggatcagtgatcgatgagccaaattggtgtgtgtactgtacaggccacaagaacgaaaatatcctctctctttaattcaggtgtgctccctgctgccggatcacggccggcccggtttggtttttggacgacggcggcgaggatcgatccaagggaggcgccgccacgccgccgcggcggtgtactttaattttcaagttgtcagctactttctgtaatttgtttcatgatggttcggtttcctgtgacagccagcacttttgttgtatgtcaaatgcaatgtatacatgatataccggttgttatcgttgttgttgctgttgttgactttgttctgtccattgatgcattgcaaggtcaaatataggagcacaataatctg</dnaseqindica>
External Link(s)	NCBI Gene:Os06g0597000, RefSeq:Os06g0597000