June 2018, Volume 60 Issue 6, Pages 445-528.

Cover Caption: Role of KNAT7 in secondary cell wall formation
KNAT7 transcription factor plays an important role in secondary cell wall biosynthesis. However, the exact function of KNAT7 is still unclear. In this issue, He et al. (514¨C528) demonstrate that KNAT7 positively regulates xylan biosynthesis, which provides a new clue to the regulation network of secondary cell wall formation.


Plant genetics enters the nano age?  
Author: Dirk Joldersma and Zhongchi Liu
Journal of Integrative Plant Biology 2018 60(6): 446-447
Published Online: February 27, 2018
DOI: 10.1111/jipb.12646

Plant transformation has for many years relied on agrobacterium infection or biolistic particle delivery. However, these two methods are limited to model plant systems or a small number of crop species. This commentary highlights recent developments in the nanoparticle©\mediated transformation that have the potential to revolutionize how plants are transformed.


Abstract (Browse 232)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Letter to the Editor
ANAPHASE PROMOTING COMPLEX/CYCLOSOME©\mediated cyclin B1 degradation is critical for cell cycle synchronization in syncytial endosperms  
Author: Lei Guo, Li Jiang, Xiu-Li Lu and Chun-Ming Liu
Journal of Integrative Plant Biology 2018 60(6): 448-454
Published Online: February 9, 2018
DOI: 10.1111/jipb.12641

Although it is known that in most angiosperms mitosis in early endosperm development is syncytial and synchronized, it is unclear how the synchronization is regulated. We showed previously that APC11, also named ZYG1, in Arabidopsis activates zygote division by interaction and degradation of cyclin B1. Here, we report that the mutation in APC11/ZYG1 led to unsynchronized mitosis and over©\accumulation of cyclin B1©\GUS in the endosperm. Mutations in two other APC subunits showed similar defects. Transgenic expression of stable cyclin B1 in the endosperm also caused unsynchronized mitosis. Further, downregulation of APC11 generated multi©\nucleate somatic cells with unsynchronized mitotic division. Together, our results suggest that APC/C©\mediated cyclin B1 degradation is critical for cell cycle synchronization.

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In most seed plants, mitotic divisions in coenocytic endosperms are synchronized. Here, we demonstrate that cell cycle synchronization is regulated by APC/C©\mediated cyclin B1 degradation in Arabidopsis.
Auxin polar transport flanking incipient primordium initiates leaf adaxial©\abaxial polarity patterning  
Author: Jiaqiang Dong and Hai Huang
Journal of Integrative Plant Biology 2018 60(6): 455-464
Published Online: February 6, 2018
DOI: 10.1111/jipb.12640

The leaves of most higher plants are polar along their adaxial©\abaxial axis, and the development of the adaxial domain (upper side) and the abaxial domain (lower side) makes the leaf a highly efficient photosynthetic organ. It has been proposed that a hypothetical signal transported from the shoot apical meristem (SAM) to the incipient leaf primordium, or conversely, the plant hormone auxin transported from the leaf primordium to the SAM, initiates leaf adaxial©\abaxial patterning. This hypothetical signal has been referred to as the Sussex signal, because the research of Ian Sussex published in 1951 was the first to imply its existence. Recent results, however, have shown that auxin polar transport flanking the incipient leaf primordium, but not the Sussex signal, is the key to initiate leaf polarity. Here, we review the new findings and integrate them with other recently published results in the field of leaf development, mainly focusing on the early steps of leaf polarity establishment.

Abstract (Browse 258)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Leaf initiates at the beginning is a round and dome©\like structure, and its flattening was previously proposed to be directed by a so©\called Sussex signal. Recent studies demonstrated that lateral auxin movement flanking the initiating leaf, but not the Sussex signal, plays a key role in initiation of leaf flattening.
          Functional Omics and Systems Biology
ZmCOL3, a CCT gene represses flowering in maize by interfering with the circadian clock and activating expression of ZmCCT
Author: Minliang Jin, Xiangguo Liu, Wei Jia, Haijun Liu, Wenqiang Li, Yong Peng, Yanfang Du, Yuebin Wang, Yuejia Yin, Xuehai Zhang, Qing Liu, Min Deng, Nan Li, Xiyan Cui, Dongyun Hao and Jianbing Yan
Journal of Integrative Plant Biology 2018 60(6): 465-480
Published Online: January 10, 2018
DOI: 10.1111/jipb.12632

Flowering time is a trait vital to the adaptation of flowering plants to different environments. Here, we report that CCT domain genes play an important role in flowering in maize (Zea mays L.). Among the 53 CCT family genes we identified in maize, 28 were located in flowering time quantitative trait locus regions and 15 were significantly associated with flowering time, based on candidate©\gene association mapping analysis. Furthermore, a CCT gene named ZmCOL3 was shown to be a repressor of flowering. Overexpressing ZmCOL3 delayed flowering time by approximately 4 d, in either long©\day or short©\day conditions. The absence of one cytosine in the ZmCOL3 3'UTR and the presence of a 551 bp fragment in the promoter region are likely the causal polymorphisms contributing to the maize adaptation from tropical to temperate regions. We propose a modified model of the maize photoperiod pathway, wherein ZmCOL3 acts as an inhibitor of flowering either by transactivating transcription of ZmCCT, one of the key genes regulating maize flowering, or by interfering with the circadian clock.

Abstract (Browse 328)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study emphasizes the important roles of CCT gene family in maize flowering time. One of them, ZmCOL3, was validated to be a repressor of flowering time, and its role was integrated into a modified model for the maize photoperiod pathway.
          Metabolism and Biochemistry
Cellulose synthase ¡®class specific regions¡¯ are intrinsically disordered and functionally undifferentiated
Author: Tess R. Scavuzzo-Duggan, Arielle M. Chaves, Abhishek Singh, Latsavongsakda Sethaphong, Erin Slabaugh, Yaroslava G. Yingling, Candace H. Haigler and Alison W. Roberts
Journal of Integrative Plant Biology 2018 60(6): 481-497
Published Online: January 30, 2018
DOI: 10.1111/jipb.12637

Cellulose synthases (CESAs) are glycosyltransferases that catalyze formation of cellulose microfibrils in plant cell walls. Seed plant CESA isoforms cluster in six phylogenetic clades, whose non©\interchangeable members play distinct roles within cellulose synthesis complexes (CSCs). A ‘class specific region’ (CSR), with higher sequence similarity within versus between functional CESA classes, has been suggested to contribute to specific activities or interactions of different isoforms. We investigated CESA isoform specificity in the moss, Physcomitrella patens (Hedw.) B. S. G. to gain evolutionary insights into CESA structure/function relationships. Like seed plants, P. patens has oligomeric rosette©\type CSCs, but the PpCESAs diverged independently and form a separate CESA clade. We showed that P. patens has two functionally distinct CESAs classes, based on the ability to complement the gametophore©\negative phenotype of a ppcesa5 knockout line. Thus, non©\interchangeable CESA classes evolved separately in mosses and seed plants. However, testing of chimeric moss CESA genes for complementation demonstrated that functional class©\specificity is not determined by the CSR. Sequence analysis and computational modeling showed that the CSR is intrinsically disordered and contains predicted molecular recognition features, consistent with a possible role in CESA oligomerization and explaining the evolution of class©\specific sequences without selection for class©\specific function.

Abstract (Browse 234)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The ¡®class specific region¡¯ of cellulose synthases is intrinsically disordered and contains predicted molecular recognition features, consistent with a role in complex formation. This region does not determine class specific function despite higher sequence similarity within vs. between functional classes.
          Molecular Physiology
Silencing GRAS2 reduces fruit weight in tomato  
Author: Miao Li, Xin Wang, Changxing Li, Hanxia Li, Junhong Zhang and Zhibiao Ye
Journal of Integrative Plant Biology 2018 60(6): 498-513
Published Online: January 23, 2018
DOI: 10.1111/jipb.12636

GRAS family transcription factors are involved in multiple biological processes in plants. Here, we report that GRAS2 plays a vital role in regulating fruit weight in tomato (Solanum lycopersicum). We establish that the expression of GRAS2 was elevated in ovaries and maintained at a constant level in fertilized ovules. Reduction of GRAS2 expression in transgenic plants reduced fruit weight through modulating ovary growth and cell size. At the metabolic level, downregulation of GRAS2 decreased activities of the gibberellic acid biosynthesis and signal transduction pathways, leading to insufficient levels of active gibberellic acid during the initial ovary development of tomato. Moreover, genotypic diversity of GRAS2 was consistent with the molecular basis of fruit weight evolution, suggesting that GRAS2 contributes to the molecular basis of the evolution of fruit weight in tomato. Collectively, these findings enhance our understanding of GRAS2 functions, in fruit development of tomato, and demonstrate a strong association between the GRAS gene family and fruit development.

Abstract (Browse 495)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
We analyzed the early stage of fruit development in tomato, and found that cell development and positive growth signal are crucial factors in regulating tomato fruit development. We also provided evidence to show the trace of fruit evolution in tomato.
          Plant-abiotic Interactions
KNAT7 positively regulates xylan biosynthesis by directly activating IRX9 expression in Arabidopsis
Author: Jun-Bo He, Xian-Hai Zhao, Ping-Zhou Du, Wei Zeng, Cherie T Beahan, Yu-Qi Wang, Hui-Ling Li, Antony Bacic and Ai-Min Wu
Journal of Integrative Plant Biology 2018 60(6): 514-528
Published Online: February 2, 2018
DOI: 10.1111/jipb.12638

Xylan is the major plant hemicellulosic polysaccharide in the secondary cell wall. The transcription factor KNOTTED©\LIKE HOMEOBOX OF ARABIDOPSIS THALIANA 7 (KNAT7) regulates secondary cell wall biosynthesis, but its exact role in regulating xylan biosynthesis remains unclear. Using transactivation analyses, we demonstrate that KNAT7 activates the promoters of the xylan biosynthetic genes, IRREGULAR XYLEM 9 (IRX9), IRX10, IRREGULAR XYLEM 14©\LIKE (IRX14L), and FRAGILE FIBER 8 (FRA8). The knat7 T©\DNA insertion mutants have thinner vessel element walls and xylary fibers, and thicker interfascicular fiber walls in inflorescence stems, relative to wild©\type (WT). KNAT7 overexpression plants exhibited opposite effects. Glycosyl linkage and sugar composition analyses revealed lower xylan levels in knat7 inflorescence stems, relative to WT; a finding supported by labeling of inflorescence walls with xylan©\specific antibodies. The knat7 loss©\of©\function mutants had lower transcript levels of the xylan biosynthetic genes IRX9, IRX10, and FRA8, whereas KNAT7 overexpression plants had higher mRNA levels for IRX9, IRX10, IRX14L, and FRA8. Electrophoretic mobility shift assays indicated that KNAT7 binds to the IRX9 promoter. These results support the hypothesis that KNAT7 positively regulates xylan biosynthesis.

Abstract (Browse 237)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
KNAT7, as a transcription factor repressor, has been shown to negatively regulate secondary cell wall biosynthesis. In this study, we demonstrate that KNAT7 positively regulates xylan biosynthesis, which is one of the main components of secondary cell wall, by activating xylan biosynthesis genes IRX9, IRX10, IRX14L and FRA8.
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