Biomedical subjects

Qian-Hao Zhu

Publications and source records attributed to Qian-Hao Zhu.

5 recordsLinked to original sources

PubMed2006

Compact shoot and leafy head 1, a mutation affects leaf initiation and developmental transition in rice (Oryza sativa L).

The shoot apical meristem (SAM) produces lateral organs in a regular spacing (phyllotaxy) and at a regular interval (phyllochron) during the vegetative phase. In a Dissociation (Ds) insertion rice population, we identified a mutant, compact shoot and leafy head 1 (csl1), which produced massive number of leaves (~70) during the vegetative phase. In csl1, the transition from the vegetative to the reproductive phase was delayed by about 2 months under long-day conditions. With a reduced leaf size and severe dwarfism, csl1 failed to produce a normal panicle after the transition to reproductive growth. Instead, it produced a leafy panicle, in which all primary rachis-branches were converted to vegetative shoots. Phenotypically csl1 resembled pla mutants in short plastochron but was more severe in the conversion of the reproductive organs to vegetative organs. In addition, neither the expression nor the coding region of PLA1 or PLA2 was affected in csl1. csl1 is most likely a dominant mutation because no mutant segregant was observed in progeny of 67 siblings of the csl1 mutant. CSL1 may represent a novel gene, which functions downstream of PLA1 and/or PLA2, or alternatively functions in a separate pathway, involved in the regulation of leaf initiation and developmental transition via plant hormones or other mobile signals.

Gene Expression Regulation, Developmental↗

PubMed2006

Dissociation (Ds) constructs, mapped Ds launch pads and a transiently-expressed transposase system suitable for localized insertional mutagenesis in rice.

We have developed a transiently-expressed transposase (TET)-mediated Dissociation (Ds) insertional mutagenesis system for generating stable insertion lines in rice which will allow localized mutagenesis of a chromosomal region. In this system, a Ds containing T-DNA construct was used to produce Ds launch pad lines. Callus tissues, from single-copy Ds/T-DNA lines, were then transiently infected with Agrobacterium harbouring an immobile Ac (iAc) construct, also containing a green fluorescent protein gene (sgfpS65T) as the visual marker. We have regenerated stable Ds insertion lines at a frequency of 9-13% using selection for Ds excision and GFP counter selection against iAc and nearly half of them were unique insertion lines. Double transformants (iAc/Ds) were also obtained and their progeny yielded approximately 10% stable insertion lines following excision and visual marker screening with 50% redundancy. In general, more than 50% of the Ds reinsertions were within 1 cM of the launch pad. We have produced a large number of single-copy Ds/T-DNA launch pads distributed over the rice chromosomes and have further refined the Ds/T-DNA construct to enrich for "clean" single-copy T-DNA insertions. The availability of single copy "clean" Ds/T-DNA launch pads will facilitate chromosomal region-directed insertion mutagenesis. This system provides an opportunity for distribution of gene tagging tasks among collaborating laboratories on the basis of chromosomal locations.

Chromosome Mapping↗

PubMed2005

Isolation and characterization of a Ds-tagged rice (Oryza sativa L.) GA-responsive dwarf mutant defective in an early step of the gibberellin biosynthesis pathway.

We have isolated a severe dwarf transposon (Ds) insertion mutant in rice (Oryza sativa L.), which could be differentiated early in the seedling stage by reduced shoot growth and dark green leaves, and later by severe dwarfism and failure to initiate flowering. These mutants, however, showed normal seed germination and root growth. One of the sequences flanking Ds, rescued from the mutant, was of a chromosome 4-located putative ent-kaurene synthase (KS) gene, encoding the enzyme catalyzing the second step of the gibberellin (GA) biosynthesis pathway. Dwarf mutants were always homozygous for this Ds insertion and no normal plants homozygous for this mutation were recovered in the segregating progeny, indicating that the Ds insertion mutation is recessive. As mutations in three recently reported rice GA-responsive dwarf mutant alleles and the dwarf mutation identified in this study mapped to the same locus, we designate the corresponding gene OsKS1. The osks1 mutant seedlings were responsive to exogenous gibberellin (GA3). OsKS1 transcripts of about 2.3 kb were detected in leaves and stem of wild-type plants, but not in germinating seeds or roots, suggesting that OsKS1 is not involved in germination or root growth. There are at least five OsKS1-like genes in the rice genome, four of which are also represented in rice expressed sequence tag (EST) databases. All OsKS1-like genes are transcribed with different expression patterns. ESTs corresponding to all six OsKS genes are represented in other cereal databases including barley, wheat and maize, suggesting that they are biologically active.

Alkyl and Aryl Transferases↗

PubMed2004

The ANTHER INDEHISCENCE1 gene encoding a single MYB domain protein is involved in anther development in rice.

Using a two-element iAc/Ds transposon-tagging system, we identified a rice (Oryza sativa L. cv Nipponbare) recessive mutant, anther indehiscence1 (aid1), showing partial to complete spikelet sterility. Spikelets of the aid1 mutant could be classified into three types based on the viability of pollen grains and the extent of anther dehiscence. Type 1 spikelets (approximately 25%) were sterile due to a failure in accumulation of starch in pollen grains. Type 2 spikelets (approximately 55%) had viable pollen grains, but anthers failed to dehisce and/or synchronize with anthesis due to failure in septum degradation and stomium breakage, resulting in sterility. Type 3 spikelets (approximately 20%) had normal fertility. In addition, aid1 mutant plants had fewer tillers and flowered 10 to 15 d later than the wild type. The Ds insertion responsible for the aid1 mutation was mapped within the coding region of the AID1 gene on chromosome 6, which is predicted to encode a novel protein of 426 amino acids with a single MYB domain. The MYB domain of AID1 is closely related to that of the telomere-binding proteins of human, mouse, and Arabidopsis, and of single MYB domain transcriptional regulators in plants such as PcMYB1 and ZmIBP1. AID1 was expressed in both the leaves and panicles of wild-type plants, but not in mutant plants.

Amino Acid Sequence↗

PubMed2003

Ds tagging of BRANCHED FLORETLESS 1 (BFL1) that mediates the transition from spikelet to floret meristem in rice (Oryza sativa L).

BACKGROUND: The genetics of spikelet formation, a feature unique to grasses such as rice and maize, is yet to be fully understood, although a number of meristem and organ identity mutants have been isolated and investigated in Arabidopsis and maize. Using a two-element Ac/Ds transposon tagging system we have isolated a rice mutant, designated branched floretless 1 (bfl1) which is defective in the transition from spikelet meristem to floret meristem. RESULTS: The bfl1 mutant shows normal differentiation of the primary rachis-branches leading to initial spikelet meristem (bract-like structure equivalent to rudimentary glumes) formation but fails to develop empty glumes and florets. Instead, axillary meristems in the bract-like structure produce sequential alternate branching, thus resulting in a coral shaped morphology of the branches in the developing panicle. The bfl1 mutant harbours a single Ds insertion in the upstream region of the BFL1 gene on chromosome 7 corresponding to PAC clone P0625E02 (GenBank Acc No. message URL http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=nucleotide&list_uids=34395191&dopt=GenBank&term=ap004570AP004570). RT-PCR analyses revealed a drastic reduction of BFL1 transcript levels in the bfl1 mutant compared to that in the wild-type. In each of the normal panicle-bearing progeny plants, from occasional revertant seeds of the vegetatively-propagated mutant plant, Ds was shown to be excised from the bfl1 locus. BFL1 contains an EREBP/AP2 domain and is most likely an ortholog of the maize transcription factor gene BRANCHED SILKLESS1 (BD1). CONCLUSIONS: bfl1 is a Ds-tagged rice mutant defective in the transition from spikelet meristem (SM) to floret meristem (FM). BFL1 is most probably a rice ortholog of the maize ERF (EREBP/AP2) transcription factor gene BD1. Based on the similarities in mutant phenotypes bfl1 is likely to be an allele of the previously reported frizzy panicle locus.

Amino Acid Sequence↗