October 2017, Volume 59 Issue 10, Pages 709每771.


Cover Caption: Nutrient use efficiency in crops
Improving nutrient efficiency is important for agricultural sustainability. In the invited review article written by Chen and Liao (pp. 710每735), it is proposed that integrations of nutrient acquisition, translocation, remobilization and metabolic efficiency may help crops to achieve a higher nutrient use efficiency, and the strategies that can be used.

 

          Invited Expert Review
Engineering crop nutrient efficiency for sustainable agriculture  
Author: Liyu Chen and Hong Liao
Journal of Integrative Plant Biology 2017 59(10): 710每735
Published Online: June 10, 2017
DOI: 10.1111/jipb.12559
      
    

Increasing crop yields can provide food, animal feed, bioenergy feedstocks and biomaterials to meet increasing global demand; however, the methods used to increase yield can negatively affect sustainability. For example, application of excess fertilizer can generate and maintain high yields but also increases input costs and contributes to environmental damage through eutrophication, soil acidification and air pollution. Improving crop nutrient efficiency can improve agricultural sustainability by increasing yield while decreasing input costs and harmful environmental effects. Here, we review the mechanisms of nutrient efficiency (primarily for nitrogen, phosphorus, potassium and iron) and breeding strategies for improving this trait, along with the role of regulation of gene expression in enhancing crop nutrient efficiency to increase yields. We focus on the importance of root system architecture to improve nutrient acquisition efficiency, as well as the contributions of mineral translocation, remobilization and metabolic efficiency to nutrient utilization efficiency.

Abstract (Browse 207)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Improving crop nutrient efficiency can improve agricultural sustainability by increasing yield with lower environmental costs. Here, we summarized the mechanisms and strategies to increase nutrient efficiency, focused on the contributions of root system architecture to acquisition efficiency, as well as mineral translocation, remobilization, and metabolic efficiency to utilization efficiency.
          Letters to the Editor
Mutation in a novel gene SMALL AND CORDATE LEAF 1 affects leaf morphology in cucumber  
Author: Dongli Gao, Chunzhi Zhang, Shu Zhang, Bowen Hu, Shenhao Wang, Zhonghua Zhang and Sanwen Huang
Journal of Integrative Plant Biology 2017 59(10): 736每741
Published Online: June 9, 2017
DOI: 10.1111/jipb.12558
      
    

Plant species exhibit substantial variation in leaf morphology. We isolated a recessive mutant gene termed small and cordate leaf 1 (scl1) that causes alteration in both leaf size and shape of cucumber. Compared to wild type leaves, the scl1 mutant had fewer numbers of epidermal pavement cells. A single nucleotide polymorphism was associated with this leaf phenotype, which occurred in a putative nucleoside bisphosphate phosphatase. RNA-seq analysis of the wild type and scl1 mutant leaves suggested that SCL1 regulation may not involve known hormonal pathways. Our work identified a candidate gene for SCL1 that may play a role in leaf development.

Abstract (Browse 204)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The size and shape of leaves are important factors influencing the success of plants and agricultural productivity. This work identified a mutant locus small and cordate leaf 1 (scl1) that causes the alteration of leaf size and shape in cucumber.
Arabidopsis TOR signaling is essential for sugar-regulated callus formation  
Author: Kyounghee Lee and Pil Joon Seo
Journal of Integrative Plant Biology 2017 59(10): 742每746
Published Online: June 17, 2017
DOI: 10.1111/jipb.12560
      
    

Dedifferentiation is a remarkable process that produces pluripotent stem cells from differentiated somatic cells to ensure developmental plasticity. Plants have evolved the ability of cellular dedifferentiation, and signaling cascades related to auxin and cytokinin-dependent callus formation have been extensively investigated. However, the molecular mechanism underlying sugar-dependent callus formation remains unknown. Here, we show that sugar-dependent callus formation is mainly regulated by the TOR-E2Fa module in Arabidopsis. Sugar-activated TOR kinase phosphorylates and stabilizes E2Fa proteins to transcriptionally activate S-phase genes during callus formation. In parallel, E2Fa is transcriptionally regulated by the ARF-LBD transcription cascade. Multi-layered regulation of E2Fa by sugar and auxin is likely to shape balanced cellular dedifferentiation capability in Arabidopsis.

Abstract (Browse 181)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
As an early step of cellular dedifferentiation, tissue explants induce pluripotent cell mass callus. Callus formation involves active cell division and requires sugar signaling. This study demonstrates that sugar supply is essential for robust callus formation, and sugar-dependent callus formation is mainly regulated by TOR-E2Fa module in Arabidopsis.
          Cell and Developmental Biology
ARR12 promotes de novo shoot regeneration in Arabidopsis thaliana via activation of WUSCHEL expression  
Author: Xuehuan Dai, Zhenhua Liu, Meng Qiao, Juan Li, Shuo Li and Fengning Xiang
Journal of Integrative Plant Biology 2017 59(10): 747每758
Published Online: July 5, 2017
DOI: 10.1111/jipb.12567
      
    

Auxin and cytokinin direct cell proliferation and differentiation during the in vitro culture of plant cells, but the molecular basis of these processes, especially de novo shoot regeneration, has not been fully elucidated. Here, we describe the regulatory control of shoot regeneration in Arabidopsis thaliana (L.) Heynh, based on the interaction of ARABIDOPSIS RESPONSE REGULATOR12 (ARR12) and WUSCHEL (WUS). The major site of ARR12 expression coincided with the location where the shoot apical meristem (SAM) initiated. The arr12 mutants showed severely impaired shoot regeneration and reduced responsiveness to cytokinin; consistent with this, the overexpression of ARR12 enhanced shoot regeneration. Certain shoot meristem specification genes, notably WUSCHEL (WUS) and CLAVATA3, were significantly downregulated in the arr12 explants. Chromatin immunoprecipitation (ChIP) and transient activation assays demonstrated that ARR12 binds to the promoter of WUS. These observations indicate that during shoot regeneration, in vitro, ARR12 functions as a molecular link between cytokinin signaling and the expression of shoot meristem specification genes.

Abstract (Browse 139)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
In the arr12 mutant, shoot regeneration was severely impaired and its responsiveness to cytokinin was greatly reduced. ARR12 can directly activate WUS via binding WUS promoter in in vitro culture. Thus ARR12 functions as a link connecting cytokinin signaling with the specification of apical/shoot fate during shoot regeneration.
          Plant-environmental Interactions
Localized micronutrient patches induce lateral root foraging and chemotropism in Nicotiana attenuata
Author: Abigail P. Ferrieri, Ricardo A.R. Machado, Carla C.M. Arce, Danny Kessler, Ian T. Baldwin and Matthias Erb
Journal of Integrative Plant Biology 2017 59(10): 759每771
Published Online: June 26, 2017
DOI: 10.1111/jipb.12566
      
    

Nutrients are distributed unevenly in the soil. Phenotypic plasticity in root growth and proliferation may enable plants to cope with this variation and effectively forage for essential nutrients. However, how micronutrients shape root architecture of plants in their natural environments is poorly understood. We used a combination of field and laboratory-based assays to determine the capacity of Nicotiana attenuata to direct root growth towards localized nutrient patches in its native environment. Plants growing in nature displayed a particular root phenotype consisting of a single primary root and a few long, shallow lateral roots. Analysis of bulk soil surrounding the lateral roots revealed a strong positive correlation between lateral root placement and micronutrient gradients, including copper, iron and zinc. In laboratory assays, the application of localized micronutrient salts close to lateral root tips led to roots bending in the direction of copper and iron. This form of chemotropism was absent in ethylene and jasmonic acid deficient lines, suggesting that it is controlled in part by these two hormones. This work demonstrates that directed root growth underlies foraging behavior, and suggests that chemotropism and micronutrient-guided root placement are important factors that shape root architecture in nature.

Abstract (Browse 122)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
We employed field and laboratory assays to determine the capacity of wild tobacco (Nicotiana attenuata) to detect and direct root growth towards localized nutrient patches. Our findings demonstrate that directed root growth underlies foraging behavior, and that chemotropism and micronutrient-guided root placement are important factors shaping root architecture in nature.
 

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