Global food security is one of the biggest challenges facing world agriculture. Significant improvements in crop yields are urgently required to meet the 50% increase in world population by 2050. Root architecture impacts the efficient uptake of nutrients, minerals and water from the soil. A greater understanding of the molecular and cellular mechanisms that control root architectural traits like root hair development (Bhosale et al Nature Communications 2018; Giri et al Nature Communications, 2018), lateral root development (Swarup et al 2008, Nature cell Biology, 10, 946-954) and root gravitropism (Swarup et al Science, 2006; Swarup et al Nature Cell Biology 2005) are likely to identify key regulators that may provide the tools to design novel strategies for future crop improvement programmes. My group is working on various aspects of root development programmes including the role of biostimulants in promoting root growth (Rossal et al 2016, Acta Horticulturae) as summarised below-
As part of a BBSRC-LINK grant, Swarup group is currently working with Six industrial partners to investigate the effect of phosphite on root development.
Phosphite represents a reduced form of phosphate that belongs to a new class of crop growth promoting chemicals termed biostimulants. Foliar application of phosphite enhances root growth and development in a range of plant species, typically increasing biomass by 30%.
Phosphite cannot be converted to phosphate, so does not enhance plant growth via a nutritional mechanism. This BBSRC LINK research programme aims to identify the mechanism(s) through which phosphites promote root growth. We are employing a multidisciplinary approach involving a combination of various 'omic', cell biology, plant physiology and CT imaging techniques. RNAseq and hormone profiling have identified several promising mechanisms that are under investigation currently.
In parallel, the six industrial partners and ourselves are also exploring the physiological basis for phosphite's ability to improve resource use efficiency and crop establishment. Our partners are testing different formulations, doses and their effect in a range of crops and in different agro-climatic conditions in several different countries including UK, Spain, Italy, Germany, Czech Republic, Finland, Canada and Brazil. By optimising doses, timing of application and treatments this project will provide a clear framework for phosphite treatment in a number of crops. With crops yielding better returns, this research is likely to have a direct impact on farm income leading to improved nutritional, financial and social stability.
By having a better understanding of the molecular and physiological role of phosphite in improving root architecture, this research proposal is likely to have a direct impact in improving resource use efficiency and plant fitness in a number of commercially important horticultural and cereal crops. This allows us to enter a new area of precision farming where traits may be deliberately manipulated via application of non-harmful chemicals.
In recent years it is emerging that regulatory long and small non protein coding RNAs (npcRNAs) are major players in regulating plant responses to biotic and abiotic stresses. In contrast to small RNAs, much less is known about the large population of long npcRNAs. In plants, they have been implicated in the regulation of mRNA transcription, localisation and translation during different processes as nodulation, flowering time and flower development, abiotic stress responses and sex chromosome-specific expression. A greater understanding of npcRNAs and their role in regulating root architectural traits like lateral root development are likely to identify key regulators that may provide the tools to design novel strategies for future crop improvement programmes. As an ongoing collaboration between our group and Martin Crespi group at ISV, Gif, France, we are performing an in depth analysis of npcRNAs during LR formation to get an insight into how they regulate LR formation and responses to several abiotic and biotic stresses.
My work on AXR4 ((Dharamsiri and Swarup et al, 2006, Science, 318, 1218-1220) has identified a novel class of endoplasmic reticulum protein in plants that regulate targeting of multi membrane spanning proteins. Such proteins form a very important class of proteins that regulate many important physiological and biochemical processes and can have profound impact on plant growth and development. Currently, my group is investigating the role of AXR4 in regulating the trafficking of members of the AUX/LAX gene family (Swarup and Péret, 2012, Frontiers in Plant Science 3, 225-229). We are also investigating the role of AXR4 in rice. We are currently creating CRISPR mutants to investigate the role of AXR4 in rice development.
Mohammed U, Caine RS, Atkinson JA, Wells D, Chater CC, Gray JE, Swarup R, Murchie EH (2018) Rice plants overexpressing OsEPF2 show reduced stomatal density and increased root cortical aerenchyma formation. Scientific Report (Nature) In Press.
Caine RS, Sloan J, Harrison EL, Mohammed U, Fulton T, Biswal AK, Dionora J, Chater CC, Coe RA, Bandyopadhyay A, Murchie E, Swarup R, Quick P and Gray JE (2018) Rice with reduced stomatal density conserves water and has improved drought tolerance under future climate conditions. New Phytologist, 221, 371-384.
Bhosale R, Giri J, Pandey BK, Giehl RFH, Hartmann A, Traini R, Truskina J, Leftley N, Hanlon M, Swarup K, Rashed A, Voß U, Alonso J, Stepanova A, Yun J, Ljung K, Brown KM, Lynch JP, Dolan L, Vernoux T, Bishopp A, Wells D, von Wirén N, Bennett MJ and Swarup R (2018) A mechanistic framework for auxin dependent Arabidopsis root hair elongation to low external phosphate. Nature Communications 9, 1409.
Giri J, Bhosale R, Huang G, Pandey BK, Parker H, Zappala S, Yang J, Dievart A, Bureau C, Ljung K, Price A, Rose T, Larrieu A, Mairhofer S, Sturrock CJ, White P, Dupuy L, Hawkesford M, Perin C, Liang W, Peret B, Hodgman CT, Lynch J, Wissuwa M, Zhang D, Pridmore T, Mooney SJ, Guiderdoni E, Swarup R and Bennett MJ (2018) Rice auxin influx carrier OsAUX1 facilitates root hair elongation in response to low external phosphate. Nature Communications 9, 1408.
Muller L, Bennett MJ, French A, Wells DM and Swarup R (2018) Root Gravitropism: Quantification, Challenges and Solutions. Methods in Molecular Biology, 1761, 103-112.
Rossall S, Qing C, Paneri M, Bennett M and Swarup R (2016) A 'growing' role for phosphites in promoting plant growth and development. Acta Hortic 1148, 61-67.
Swarup R, Crespi M and Bennett M (2016) One gene, many proteins: Mapping cell-specific alternative splicing in plants. Dev Cell, 39, 383-385.
Sato EM, Hijazi H, Bennett MJ, Vissenberg K, Swarup R (2015) New insights into root gravitropic signalling. J Exp Bot, 66, 2155-2165.
Swarup R and Bennett MJ (2014) Auxin Transport: Providing plants with a new sense of direction. Biochemist 36, 12-16.
Boutté Y, Jonsson K, McFarlane H, Johnson E, Gendre D, Swarup R, Friml J, Samuels J, Robert S and Bhalerao R (2013) ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation. Proc Natl Acad Sci, USA, 110, 16259-16264.
Peret B, Yang Y, Swarup K, James N, Ferguson A, Casimiro I, Perry P, Syed A, Laplaze L, Bennett M, Murphy A, Nielsen E and Swarup R (2012) AUX/LAX genes encode a family of auxin influx transporters that perform distinct function during Arabidopsis development. Plant Cell, 24, 2874-2885.
Swarup R, Swarup K, Benková E, Casimiro I, Péret B, Yang Y, Parry G, et al (2008) The auxin influx carrier LAX3 promotes lateral root emergence. Nature Cell Biol, 10, 946-954.
Swarup R, Dharmasiri S, Mockaitis K, Dharmasiri N, Singh S, Kowalchyk A, Marchant A, Mills S, Sandberg G, Bennett M and Estelle M (2006) AXR4 is required for localisation of AUX1. Science, 312, 1218-1220.
Swarup R, Kramer E, Perry P, Knox K, Leyser HMO, Haseloff J, Beemster G, Bhalerao R and Bennett M (2005) Root gravitropism requires lateral root cap and epidermal cells for transport and response to a mobile auxin signal. Nature Cell Biol, 7, 1057-1065.
Swarup R, Kargul J, Marchant A, Zadik D, Rahman A, Mills R, Yemm A, May S, Williams L, Millner P, Tsurumi S, Moore I, Napier R, Kerr ID and Bennett MJ 2004 Structure-Function Analysis of the presumptive Arabidopsis Auxin Permease AUX1. Plant Cell, 14, 3069-3083.
Swarup R and Bennett MJ (2003) Auxin transport: the fountain of life in plants? Dev Cell, 5, 1-2.
Swarup R, Parry G, Graham N, Allen T and Bennett M J (2002) Auxin cross-talk: integration of signalling pathways to control plant development. Plant Mol Biol, 49, 411-426.
Swarup R, Friml J, Marchant A, Ljung K, Sandberg G, Palme K and Bennett MJ (2001) Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex. Genes Dev, 15, 2648-2653.
Plant hormone auxin is crucial for plant growth and development. We mapped the tissues required for auxin transport and auxin response during root gravitropism (Swarup et al, 2005, Nature Cell Biology, 7, 1057-1065). This study revealed that epidermis is the primary site for auxin action during root gravitropism.