May 2011, Volume 53 Issue 5, Pages 338ĘC408.

Cover Caption: The Arabidopsis Seed Coat
About the cover: Seed mucilage, consisting of carbohydrate-based pectin, is synthesized by seed epidermal cells, and deposited beneath the outer cell wall. The surface of dry seeds shows volcano-like individual epidermal cells (cover photo courtesy of Courtney Hollender). In page 399ĘD408 of this issue, Bui et al. identified transcriptional co-repressor LEUNIG_HOMOLOG (LUH) as a regulator of seed mucilage extrusion. In luh mutants, the mucilage fails to break out, possibly due to altered mucilage modifications.


          Cell and Developmental Biology
Genetic Analysis of Two Weak Dormancy Mutants Derived from Strong Seed Dormancy Wild Type Rice N22 (Oryza sativa)  
Author: Bingyue Lu, Kun Xie, Chunyan Yang, Long Zhang, Tao Wu, Xi Liu, Ling Jiang and Jianmin Wan
Journal of Integrative Plant Biology 2011 53(5): 338-346
Published Online: March 21, 2011
DOI: 10.1111/j.1744-7909.2011.01038.x

Two weak dormancy mutants, designated Q4359 and Q4646, were obtained from the rice cultivar N22 after treatment with 400 Gy 60Co gamma-radiation. Compared to the N22 cultivar, the dormancy of the mutant seeds was more readily broken when exposed to a period of room temperature storage. The mutants also showed a reduced level of sensitivity to abscisic acid compared to the N22 cultivar, although Q4359 was more insensitive than Q4646. A genetic analysis indicated that in both mutants, the reduced dormancy trait was caused by a single recessive allele of a nuclear gene, but that the mutated locus was different in each case. The results of quantitative trait locus (QTL) mapping, based on the F2 population from Q4359 x Nanjing35, suggested that Q4359 lacks the QTL qSdn-1 and carries a novel allele at QTL qSdn-9, while a similar analysis of the Q4646 x Nanjing35 F2 population suggested that Q4646 lacks QTL qSdn-5, both qSdn-1 and qSdn-5 are major effect seed dormancy QTL in N22. Therefore, these two mutants were helpful to understand the mechanism of seed dormancy in N22.

Lu B, Xie K, Yang C, Zhang L, Wu T, Liu X, Jiang L, Wan J (2011) Genetic analysis of two weak dormancy mutants derived from strong seed dormancy wild type rice N22 (Oryza sativa). J. Integr. Plant Biol. 53(5), 338–346.

Abstract (Browse 2789)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Metabolism and Biochemistry
Characterization of a Novel Annexin Gene from Cotton (Gossypium hirsutum cv CRI 35) and Antioxidative Role of its Recombinant Protein
Author: Lu Zhou, Jin Duan, Xiao-Ming Wang, Heng-Mu Zhang, Ming-Xing Duan and Jin-Yuan Liu
Journal of Integrative Plant Biology 2011 53(5): 347-357
Published Online: February 23, 2011
DOI: 10.1111/j.1744-7909.2011.01034.x

Plant annexins represent a multigene family involved in cellular elongation and development. A cDNA encoding a novel annexin was isolated from a cotton (Gossypium hirsutum) fiber cDNA library and designated GhAnx1. This gene encodes a 316 amino acid protein with a theoretical molecular mass of 36.06 kDa and a theoretical pI of 6.19. At the amino acid level, it shares high sequence similarity and has evolutionary relationships with annexins from higher plants. The purified recombinant protein expressed in Escherichia coli was used to investigate its physicochemical properties. Circular dichroism spectrum analyses showed a positive peak rising to the maximum at 196 nm and a broad negative band rounding 215 nm, suggesting that the GhAnx1 protein was prominently α-helical. The fluorescence measurements indicated that it could bind to Ca2+in vitro. These results demonstrated that GhAnx1 was a typical annexin protein in cotton. A bioassay experiment was conducted to analyze its potential function and showed that E. coli cells expressing GhAnx1 were protected from tert-butyl hydroperoxide (tBH) stress, suggesting that it had a potential antioxidative role. Northern blot analyses revealed that GhAnx1 was highly expressed in fibers, especially during the elongation stage, suggesting that it might be important for fiber elongation.

Zhou L, Duan J, Wang XM, Zhang HM, Duan MX, Liu JY (2011) Characterization of a novel annexin gene from cotton (Gossypium hirsutum cv CRI 35) and antioxidative role of its recombinant protein. J. Integr. Plant Biol. 53(5), 347–357.

Abstract (Browse 1729)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant-environmental Interactions
Microarray Expression Profiling of Postharvest Ponkan Mandarin (Citrus reticulata) Fruit under Cold Storage Reveals Regulatory Gene Candidates and Implications on Soluble Sugars Metabolism
Author: Andan Zhu, Wenyun Li, Junli Ye, Xiaohua Sun, Yuduan Ding, Yunjiang Cheng and Xiuxin Deng
Journal of Integrative Plant Biology 2011 53(5): 358-374
Published Online: February 23, 2011
DOI: 10.1111/j.1744-7909.2011.01035.x

Low temperature storage is widely applied to maintain citrus postharvest fruit quality. In this study, the transcriptional and metabolic changes in the pulp tissue of Citrus reticulata Blanco cv. “Ponkan” were studied for three successive months under cold storage by Affymetrix Citrus GeneChip and gas chromatography, respectively. As many as 2 161 differentially expressed transcripts were identified based on the bayesian hierarchical model. The statistical analysis of gene ontology revealed that defense/stress-related genes were induced quickly, while autophagy-related genes were overrepresented in the late sampling stages, suggesting that the functional shift may coincide with the subsequent steps of chilling development. We further classified the potential regulatory components and concluded that ethylene may play the crucial role in chilling development in this non-climacteric fruit. To cope with complex events, 53 upregulated transcription factors represented regulatory candidates. Within these, the AP2-EREBP, C2H2 and AS2 gene family were overrepresented. Cold storage also causes alterations in various metabolic pathways; a keen interest is paid in deciphering expression changes of soluble sugar genes as increased evidence that soluble sugars act as both osmolytes and metabolite signal molecules. Our results will likely facilitate further studies in this field with promising genetic candidates during chilling.

Zhu A, Li W, Ye J, Sun X, Ding Y, Cheng Y, Deng X (2011) Microarray expression profiling of postharvest Ponkan mandarin (Citrus reticulata) fruit under cold storage reveals regulatory gene candidates and implications on soluble sugars metabolism. J. Integr. Plant Biol. 53(5), 358–374.

Abstract (Browse 2066)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Overexpression of SGR Results in Oxidative Stress and Lesion-mimic Cell Death in Rice Seedlings
Author: Huawu Jiang, Yaping Chen, Meiru Li, Xinglan Xu and Guojiang Wu
Journal of Integrative Plant Biology 2011 53(5): 375-387
Published Online: March 7, 2011
DOI: 10.1111/j.1744-7909.2011.01037.x

It is thought that the Stay Green Rice (SGR) gene is involved in the disaggregation of the light harvesting complex and in the subsequent breakdown of chlorophyll and apo-protein during senescence. In this study, we found that overexpression of SGR (Ov-SGR) resulted in the generation of singlet oxygen and other reactive oxygen species and produced a chlorophyll-dependent regional cell death phenotype on leaves of rice seedlings. Transcriptome analyses using Affymetrix Rice GeneChips revealed that Ov-SGR rice seedlings exhibited a number of signs of singlet oxygen response. The genes and their associated biochemical pathways identified provide an insight into how rice plants respond to singlet oxygen at the molecular and physiologic level.

Jiang H, Chen Y, Li M, Xu X, Wu G (2011) Overexpression of SGR results in oxidative stress and lesion-mimic cell death in rice seedlings. J. Integr. Plant Biol. 53(5), 375–387.

Abstract (Browse 2749)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant Reproduction Biology
Roles of Carbohydrate Supply and Ethylene, Polyamines in Maize Kernel Set
Author: Han-Yu Feng, Zhi-Min Wang, Fan-Na Kong, Min-Jie Zhang and Shun-Li Zhou
Journal of Integrative Plant Biology 2011 53(5): 388-398
Published Online: March 22, 2011
DOI: 10.1111/j.1744-7909.2011.01039.x

Glucose appears to have an antagonistic relationship with ethylene and ethylene and polyamines appear to play antagonistic roles in the abortion of seeds and fruits. Moreover, ethylene, spermidine, and spermine share a common biosynthetic precursor. The synchronous changes of them and the relationships with kernel set are currently unclear. Here, we stimulated maize (Zea mays L.) apical kernel set and studied their changes at 4, 8, 12, and 16 d after pollination (DAP). The status of the apical kernels changed from abortion to set, showing a pattern similar to that of the middle kernels, with slow decrease in glucose and rapid decline in ethylene production, and a sharp increase in spermidine and spermine after four DAP. Synchronous changes in ethylene and spermidine were also observed. However, the ethylene production decreased slowly in the aborted apical kernels, the glucose and polyamines concentrations were lower. Ethephon application did not block the change from abortion to set for the setting apical kernels. These data indicate that the developmental change may be accompanied by an inhibition of adequate glucose to ethylene synthesis and subsequent promotion of spermidine and spermine synthesis, and adequate carbohydrate supply may play a key role in the developmental process.

Feng HY, Wang ZM, Kong FN, Zhang MJ, Zhou SL (2011) Roles of carbohydrate supply and ethylene, polyamines in maize kernel set. J. Integr. Plant Biol. 53(5), 388–398.

Abstract (Browse 2432)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
LEUNIG_HOMOLOG and LEUNIG Regulate Seed Mucilage Extrusion in Arabidopsis  
Author: Minh Bui, Nathan Lim, Paja Sijacic and Zhongchi Liu
Journal of Integrative Plant Biology 2011 53(5): 399-408
Published Online: March 1, 2011
DOI: 10.1111/j.1744-7909.2011.01036.x

LEUNIG (LUG) and LEUNIG_HOMOLOG (LUH) encode two closely related Arabidopsis proteins, belonging to the Gro/TLE family of transcriptional co-repressors. These two genes were previously shown to exhibit partially overlapping functions in embryo and flower development. In this report, the role of both LUH and LUG on seed mucilage extrusion was examined. Seed mucilage extrusion occurs after the seeds are imbibed, serving as functional aid in seed hydration, germination, and dispersal. While luh-1 mutants exhibited strong defects in seed mucilage extrusion, lug-3 mutants exhibited a minor phenotype in mucilage extrusion. Further characterization indicates that luh-1 does not exhibit any obvious defect in seed epidermal cell differentiation, mucilage synthesis, or mucilage deposition, suggesting a specific role of LUH in mucilage extrusion. This seed mucilage phenotype of luh-1 is identical to that of mucilage modified 2 (mum2) mutants. MUM2 encodes a β-galactosidase required for the modification of the mucilage. Quantitative reverse transcription polymerase chain reaction of RNA extracted from siliques detected a slight decrease of MUM2 mRNA in the luh-1 mutant compared to the wild type. Together, LUH and possibly LUG may specifically regulate mucilage extrusion by promoting the expression of genes required for mucilage maturation.

Bui M, Lim N, Sijacic P, Liu Z (2011) LEUNIG_HOMOLOG and LEUNIG regulate seed mucilage extrusion in Arabidopsis. J. Integr. Plant Biol. 53(5), 399–408.

Abstract (Browse 2934)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
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