The tea plant CsLHT1 and CsLHT6 transporters take up amino acids, as a nitrogen source, from the soil of organic tea plantations

Organic tea is more popular than conventional tea that originates from fertilized plants.Amino acids inorganic soils constitute a substantial pool nitrogen(N)available for plants.However,the amino-acid contents in soils of tea plantations and how tea plants take up these amino acids remain largely unknown.In this study,we show that the amino-acid content in the soil of an organic tea plantation is significantly higher than that of a conventional tea plantation.Glutamate,alanine,valine,and leucine were the most abundant amino acids in the soil of this tea plantation.When 15 N-glutamate was fed to tea plants,it was efficiently absorbed and significantly increased the contents of other amino acids in the roots.We cloned seven CsLHT genes encoding amino-acid transporters and found that the expression of CsLHT1,CsLHT2,and CsLHT6 in the roots significantly increased upon glutamate feeding.Moreover,the expression of CsLHT1 or CsLHT6 in a yeast amino-acid uptake-defective mutant,22Δ10α,enabled growth on media with amino acids constituting the sole N source.Amino-acid uptake assays indicated that CsLHT1 and CsLHT6 are H^(+)-dependent high-and low-affinity amino-acid transporters,respectively.We further demonstrated that CsLHT1 and CsLHT6 are highly expressed in the roots and are localized to the plasma membrane.Moreover,overexpression of CsLHT1 and CsLHT6 in Arabidopsis significantly improved the uptake of exogenously supplied 15 N-glutamate and 15 N-glutamine.Taken together,our findings are consistent with the involvement of CsLHT1 and CsLHT6 in amino-acid uptake from the soil,which is particularly important for tea plants grown inorganic tea plantations.

Constitutive basis of root system architecture:uncovering a promising trait for breeding nutrient-and drought-resilient crops

Root system architecture(RSA)plays a pivotal role in efficient uptake of essential nutrients,such as phosphorous(P),nitrogen(N),and water In soils with heterogeneous nutrient distribution,root plasticity can optimize acquisition and plant growth.Here,we present evidence that a constitutive RSA can confer benefits for sorghum grown under both sufficient and limiting growth conditions.Our studies,using P efficient SC103 and inefficient BTx635 sorghum cultivars,identified significant differences in root traits,with SC103 developing a larger root system with more and longer lateral roots,and enhanced shoot biomass,under both nutrient sufficient and deficient conditions.In addition to this constitutive attribute,under P deficiency,both cultivars exhibited an initial increase in lateral root development;however,SC103 still maintained the larger root biomass.Although N deficiency and drought stress inhibited both root and shoot growth,for both sorghum cultivars,SC103 again maintained the better performance.These findings reveal that SC103,a P efficient sorghum cultivar,also exhibited enhanced growth performance under N deficiency and drought.Our results provide evidence that this constitutive nature of RSA can provide an avenue for breeding nutrient-and drought-resilient crops.

Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants

As an essential plant macronutrient, the low availability of phosphorus(P) in most soils imposes serious limitation on crop production. Plants have evolved complex responsive and adaptive mechanisms for acquisition, remobilization and recycling of phosphate(Pi) to maintain P homeostasis.Spatio‐temporal molecular, physiological, and biochemical Pi deficiency responses developed by plants are the consequence of local and systemic sensing and signaling pathways. Pi deficiency is sensed locally by the root system where hormones serve as important signaling components in terms of developmental reprogramming, leading to changes in root system architecture. Root‐to‐shoot and shoot‐to‐root signals, delivered through the xylem and phloem, respectively, involving Pi itself,hormones, miRNAs, mRNAs, and sucrose, serve to coordinate Pi deficiency responses at the whole‐plant level. A combination of chromatin remodeling, transcriptional and posttranslational events contribute to globally regulating a wide range of Pi deficiency responses. In this review, recent advances are evaluated in terms of progress toward developing a comprehensive understanding of the molecular events underlying control over P homeostasis. Application of this knowledge, in terms of developing crop plants having enhanced attributes for P use efficiency, is discussed from the perspective of agricultural sustainability in the face of diminishing global P supplies.

Phloem-Mobile AuxlIAA Transcripts Target to the Root Tip and Modify Root Architecture

In plants,the phloem is the component of the vascular system that delivers nutrients and transmits signals from mature leaves to developing sink tissues.Recent studies have identified proteins,mRNA,and small RNA within the phloem sap of several plant species.It is now of considerable interest to elucidate the biological functions of these potential long-distance signal agents,to further our understanding of how plants coordinate their developmental programs at the whole-plant level.In this study,we developed a strategy for the functional analysis of phloem-mobile mRNA by focusing on IAA transcripts,whose mobility has previously been reported in melon (Cucumis melo cv.Hale's Best Jumbo).Indoleacetic acid (IAA) proteins are key transcriptional regulators of auxin signaling,and are involved in a broad range of developmental processes including root development.We used a combination of vasculature-enriched sampling and hetero-grafting techniques to identify IAA18 and IAA28 as phloem-mobile transcripts in the model plant Arabidopsis thaliana.Micro-grafting experiments were used to confirm that these IAA transcripts,which are generated in vascular tissues of mature leaves,are then transported into the root system where they negatively regulate lateral root formation.Based on these findings,we present a model in which auxin distribution,in combination with phloem-mobile Aux/IAA transcripts,can determine the sites of auxin action.

Plant lncRNAs are enriched in and move systemically through the phloem in response to phosphate deficiency

In response to phosphate(Pi) deficiency, it has been shown that micro-RNAs(miRNAs) and mRNAs are transported through the phloem for delivery to sink tissues. Growing evidence also indicates that long noncoding RNAs(lncRNAs) are critical regulators of Pi homeostasis in plants. However, whether lncRNAs are present in and move through the phloem, in response to Pi deficiency, remains to be established. Here, using cucumber as a model plant, we show that lncRNAs are enriched in the phloem translocation stream and respond,systemically, to an imposed Pi-stress. A well-known lncRNA, IPS1, the target mimic(TM) of miRNA399,accumulates to a high level in the phloem, but is not responsive to early Pi deficiency. An additional 24 miRNA TMs were also detected in the phloem translocation stream; among them miRNA171 TMs and miR166 TMs were induced in response to an imposed Pi stress.Grafting studies identified 22 lncRNAs which move systemically into developing leaves and root tips. A CU-rich PTB motif was further identified in these mobile lncRNAs. Our findings revealed that lncRNAs respond to Pi deficiency, non-cell-autonomously, and may act as systemic signaling agents to coordinate early Pi deficiency signaling, at the whole-plant level.

A Plant SMALL RNA-BINDING PROTEIN 1 Family Mediates Cell-to-Cell Trafficking of RNAi Signals

In plants,RNA interference(RNAi)plays a pivotal role in growth and development,and responses to environmental inputs,including pathogen attack.The intercellular and systemic trafficking of small interfering RNA(siRNA)/microRNA(miRNA)is a central component in this regulatory pathway.Currently,little is known with regards to the molecular agents involved in the movement of these si/miRNAs.To address this situation,we employed a biochemical approach to identify and characterize a conserved SMALL RNA-BINDING PROTEIN 1(SRBP1)family that mediates non-cell-autonomous small RNA(sRNA)trafficking.In Arabidopsis,AtSRBP1 is a glycine-rich(GR)RNA-binding protein,also known as AtGRP7,which we show binds single-stranded siRNA.A viral vector,Zucchini yellow mosaic virus(ZYMV),was employed to functionally characterized the AtSRBP1-4(AtGRP7/2/4/8)RNA recognition motif and GR domains.Cellular-based studies revealed the GR domain as being necessary and sufficient for SRBP1 cell-to-cell movement.Taken together,our findings provide a foundation for future research into the mechanism and function of mobile sRNA signaling agents in plants.

In memory of Professor Biao Ding(1960–2015)

It is with profound sadness that we mourn the loss of Dr.Biao Ding,a full-professor in the Department of Molecular Genetics,Ohio State University(OSU),and a world-renowned plant biologist with leading authority in viroid research.He died suddenly on June 26,2015 in Prague,Czech Republic,while attending the International Conference on Viroids and Viroid-Like RNAs as a Keynote Speaker.Dr.Ding was born in 1960,in Kunming,Yunnan Province,China.He received his B.S.from Beijing Forestry University in1982,and was then selected as one of the first group

Plant mineral nutrient sensing and signaling

As terrestrial plants are sessile organisms and therefore must directly deal with an often complex and changing environment,they have had to develop complex and elegant strategies to survive and thrive in the face of environmental stress.This is particularly true for plant adaptation to the soil environment,where essential mineral nutrients often are found at suboptimal levels and their concentrations can vary significantly,both spatially and temporally.Furthermore,plants also at times have to respond to excessively high and potentially toxic levels of essential nutrients,as well as toxic levels of nonessential metals and metalloids in the soil.Although plant mineral nutrition as a bona fide research discipline has a history of over 150 years,beginning with the pioneering work of Justus Von Liebieg and others in the mid‐1800’s,it is only very recently that researchers have begun to truly appreciate how sophisticated plants are with regards to the sensing of their mineral status and the maintaining of mineral homeostasis

The plant vascular system Ⅱ:From resource allocation,inter-organ communication and defense,to evolution of the monocot cambium

In this Special Issue,a focus is placed on the role of the itdxylem as an essential conduit for the long-distance Edelivery of water and mineral nutrients from the soil to the vegetative(above-ground)regions of the plant Xylem cells destined to form tracheids or vesse members,which will make up the conduit for this water and mineral transport from the roots to the shoots,undergo apoptosis,a process of

Professor Ko Shimamoto (1949–2013)

Sadly,Prof.Ko Shimamoto died on September 28,2013,aged 63.He was born in Wakayama,Japan,on October 19,1949,received his bachelor’s degree in Agriculture from Kyoto University in 1974and his PhD in Genetics from the University of Wisconsin-Madison in 1980.After his postdoctoral training at the Friedrich Miescher Institute in Basel,Switzerland,Ko returned to Japan where he took up a position in the Plantech Research Institute

The plant vascular systemⅠ:From resource allocation,inter-organ communication and defense,to evolution of the monocot cambium

In this Special Issue,a focus is placed on the role of the itdxylem as an essential conduit for the long-distance Edelivery of water and mineral nutrients from the soil to the vegetative(above-ground)regions of the plant Xylem cells destined to form tracheids or vesse members,which will make up the conduit for this water and mineral transport from the roots to the shoots,undergo apoptosis,a process of