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August 2017, Volume 59 Issue 8, Pages 525每587.

Cover Caption: Circadian clock in photosynthesis
Circadian clocks are not engineered but evolved through evolutionary tinkering by natural selection. In this issue, Joo et al. (pp. 572每587) show that the circadian clock in plants allows them to selectively pay attention to light signals rather than simple wake-up in anticipation of the rising sun. The authors measured photosynthetic rates of dark-adapted wildtype and clock-silenced plants throughout a 24-h day under field and laboratory conditions.

 

          Letters to the Editor
Natural hybridization and reproductive isolation between two Primula species  
Author: Yanping Xie, Xingfu Zhu, Yongpeng Ma, Jianli Zhao, Li Li and Qingjun Li
Journal of Integrative Plant Biology 2017 59(8): 526每530
Published Online: April 21, 2017
DOI: 10.1111/jipb.12546
      
    

Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we conducted a field survey to examine natural hybridization and reproductive isolation (RI) between sympatric populations of Primula secundiflora and P. poissonii using ten nuclear simple sequence repeat (SSR) loci. Although introgressive hybridization occurred, species boundaries between P. secundiflora and P. poissonii were maintained through nearly complete reproductive isolation. These interfertile species provide an excellent model for studying the RI mechanisms and evolutionary forces that maintain species boundaries.

Abstract (Browse 187)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Natural hybridization possibly results in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we examined natural hybridization and reproductive isolation between sympatric populations of Primula secundiflora and P. poissonii. The results suggest specific boundaries maintained well through nearly complete reproductive isolation.
Overexpression of GhFIM2 propels cotton fiber development by enhancing actin bundle formation  
Author: Min Zhang, Li-Bo Han, Wen-Yan Wang, Shen-Jie Wu, Gai-Li Jiao, Lei Su, Gui-Xian Xia and Hai-Yun Wang
Journal of Integrative Plant Biology 2017 59(8): 531每534
Published Online: May 5, 2017
DOI: 10.1111/jipb.12552
      
    

Cell elongation and secondary wall deposition are two consecutive stages during cotton fiber development. The mechanisms controlling the progression of these two developmental phases remain largely unknown. Here, we report the functional characterization of the actin-bundling protein GhFIM2 in cotton fiber. Overexpression of GhFIM2 increased the abundance of actin bundles, which was accompanied with accelerated fiber growth at the fast-elongating stage. Meanwhile, overexpression of GhFIM2 could propel the onset of secondary cell wall biogenesis. These results indicate that the dynamic rearrangement of actin higher structures involving GhFIM2 plays an important role in the development of cotton fiber cells.

Abstract (Browse 204)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study demonstrated that actin bundling protein GhFIM2 is involved in the dynamic remodeling of actin cytoskeleton in developing cotton fiber. Overexpression of GhFIM2 accelerated the fiber cell growth at the fast-elongating stage and led to an early deposition of the secondary cell wall.
          Cell and Developmental Biology
HP30-2, a mitochondrial PRAT protein for import of signal sequence-less precursor proteins in Arabidopsis thaliana
Author: Claudia Rossig, John Gray, Oscar Valdes, Sachin Rustgi, Diter von Wettstein, Christiane Reinbothe and Steffen Reinbothe
Journal of Integrative Plant Biology 2017 59(8): 535每551
Published Online: May 22, 2017
DOI: 10.1111/jipb.12555
      
    

Chloroplasts and mitochondria contain a family of putative preprotein and amino acid transporters designated PRAT. Here, we analyzed the role of two previously characterized PRAT protein family members, encoded by At3g49560 (HP30) and At5g24650 (HP30-2), in planta using a combination of genetic, cell biological and biochemical approaches. Expression studies and green fluorescent protein tagging identified HP30-2 both in chloroplasts and mitochondria, whereas HP30 was located exclusively in chloroplasts. Biochemical evidence was obtained for an association of mitochondrial HP30-2 with two distinct protein complexes, one containing the inner membrane translocase TIM22 and the other containing an alternative NAD(P)H dehydrogenase subunit (NDC1) implicated in a respiratory complex 1-like electron transport chain. Through its association with TIM22, HP30-2 is involved in the uptake of carrier proteins and other, hydrophobic membrane proteins lacking cleavable NH2-terminal presequences, whereas HP30-2's interaction with NDC1 may permit controlling mitochondrial biogenesis and activity.

Abstract (Browse 121)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Chloroplasts and mitochondria are semi-autonomous cell organelles that need to import most of their proteins from the cyotosol. Here, we report on a protein belonging to the family of preprotein and amino acid transporters designated PRAT that operates in the translocation of transit sequence-less precursor proteins into both organelle types.
          Plant-environmental Interactions
JA but not JA-Ile is the cell-nonautonomous signal activating JA mediated systemic defenses to herbivory in Nicotiana attenuata  
Author: Tohir A. Bozorov, Son Truong Dinh and Ian T. Baldwin
Journal of Integrative Plant Biology 2017 59(8): 552每571
Published Online: April 19, 2017
DOI: 10.1111/jipb.12545
      
    

The whole-plant activation of defense responses to wounding and herbivory requires systemic signaling in which jasmonates (JAs) play a pivotal role. To examine the nature of the slower cell-nonautonomous as compared to the rapid cell-autonomous signal in mediating systemic defenses in Nicotiana attenuata, reciprocal stem grafting-experiments were used with plants silenced for the JA biosynthetic gene ALLENE OXIDE CYCLASE (irAOC) or plants transformed to create JA sinks by ectopically expressing Arabidopsis JA-O-methyltransferase (ovJMT). JA-impaired irAOC plants were defective in the cell-nonautonomous signaling pathway but not in JA transport. Conversely, ovJMT plants abrogated the production of a graft-transmissible JA signal. Both genotypes displayed unaltered cell-autonomous signaling. Defense responses (17-hydroxygeranyllinalool diterpene glycosides, nicotine, and proteinase inhibitors) and metabolite profiles were differently induced in irAOC and ovJMT scions in response to graft-transmissible signals from elicited wild type stocks. The performance of Manduca sexta larvae on the scions of different graft combinations was consistent with the patterns of systemic defense metabolite elicitations. Taken together, we conclude that JA and possibly MeJA, but not JA-Ile, either directly functions as a long-distance transmissible signal or indirectly interacts with long distance signal(s) to activate systemic defense responses.

Abstract (Browse 174)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study examined the role of jasmonates in the systemic activation of defenses during herbivory, and found that JA but not JA-Ile activates systemic defenses in a cell-nonautonomous manner. This was demonstrated by the shoot grafting of WT and various JA-deficient transgenic lines in different combinations. The work also demonstrated a role for signals other than JA.
Circadian clock component, LHY, tells a plant when to respond photosynthetically to light in nature  
Author: Youngsung Joo, Variluska Fragoso, Felipe Yon, Ian T. Baldwin and Sang-Gyu Kim
Journal of Integrative Plant Biology 2017 59(8): 572每587
Published Online: April 21, 2017
DOI: 10.1111/jipb.12547
      
    

The circadian clock is known to increase plant growth and fitness, and is thought to prepare plants for photosynthesis at dawn and dusk; whether this happens in nature was unknown. We transformed the native tobacco, Nicotiana attenuata to silence two core clock components, NaLHY (irLHY) and NaTOC1 (irTOC1). We characterized growth and light- and dark-adapted photosynthetic rates (Ac) throughout a 24 h day in empty vector-transformed (EV), irLHY, and irTOC1 plants in the field, and in NaPhyA- and NaPhyB1-silenced plants in the glasshouse. The growth rates of irLHY plants were lower than those of EV plants in the field. While irLHY plants reduced Ac earlier at dusk, no differences between irLHY and EV plants were observed at dawn in the field. irLHY, but not EV plants, responded to light in the night by rapidly increasing Ac. Under controlled conditions, EV plants rapidly increased Ac in the day compared to dark-adapted plants at night; irLHY plants lost these time-dependent responses. The role of NaLHY in gating photosynthesis is independent of the light-dependent reactions and red light perceived by NaPhyA, but not NaPhyB1. In summary, the circadian clock allows plants not to respond photosynthetically to light at night by anticipating and gating red light-mediated in native tobacco.

Abstract (Browse 177)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Biological circadian clocks were not engineered but evolved through the process of evolutionary tinkering by natural selection. By measuring photosynthetic rates under field and laboratory conditions, we conclude that the plant circadian clock allows plants to selectively pay attention to light signals rather than ※when to wake up§ in anticipation of the rising sun.
 
 

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