Phosphorus and nitrogen interaction: loss of QC identity in response to P or N limitation is antecipated in pdr23 mutant

Abstract

changes in root architecture are an important adaptive strategy used by plants in response to limited nutrient availability to increase the odds of acquiring them. the quiescent center (Qc) plays an important role by altering the meristem activity causing differentiation and therefore, inducing a determinate growth program. the arabidopsis mutant pdr23 presents primary short root in the presence of nitrate and is inefficient in the use of nucleic acids as a source of phosphorus. in this study the effect of the pdr23 mutation on the Qc maintenance under low phosphorus (P) and/or nitrogen is evaluated. Qc identity is maintained in wild-type in the absence of nitrate and/or phosphate if nucleic acids can be used as an alternative source of these nutrients, but not in pdr23. the mutant is not able to use nucleic acids efficiently for substitute Pi, determinate growth is observed, similar to wild-type in the total absence of P. in the absence of N pdr23 loses the expression of Qc identity marker earlier than wild-type, indicating that not only the response to P is altered, but also to N. the data suggest that the mutation affects a gene involved either in the crosstalk between these nutrients or in a pathway shared by both nutrients limitation response. Moreover loss of Qc identity is also observed in wild-type in the absence of N at longer limitation. less drastic symptoms are observed in lateral roots of both genotypes.Key words: QC25::iudA, nutrient deficiency, root development, determinate root growth program, stress resuMo alteração na arquitetura da raiz é uma estratégia adaptativa importante, usada pelas plantas, em resposta à disponibilidade limitada de nutrientes para aumentar as chances de adquirí-los. O centro quiescente (cQ) participa na mudança da atividade meristemática, causando diferenciação e induzindo um programa determinado de crescimento. O mutante de arabidopsis pdr23 apresenta raiz primária curta na presença de nitrato e é ineficiente no uso de ácidos nucléicos como fonte de fósforo. Neste estudo, o efeito da mutação de pdr23 sobre a manutenção do cQ sob baixo fósforo e/ou nitrogênio é avaliado. Na ausência de nitrato e/ou fósforo, se ácidos nucléicos são usados como fonte alternativa destes nutrientes, a identidade do cQ é mantida na planta silvestre, mas não em pdr23. O mutante não é capaz de usar eficientemente os ácidos nucléicos como substituto de fosfato, crescimento determinado é observado, similar à planta silvestre na ausência de P. Na ausência de N, pdr23 perde a expressão do marcador de identidade do cQ antes que a planta silvestre, indicando que as respostas a P e a N estão alteradas. Os dados sugerem que a mutação em pdr23 afete um gene envolvido na interação destes nutrientes ou em uma rota usada na resposta à limitação de ambos. além disso, perda da identidade do cQ é também observada na planta silvestre na ausência de N em longos períodos. sintomas menos dramáticos são observados nas raízes laterais de ambos os genótipos.

Form matters: morphological aspects of lateral root development

“…In a few cases missing internal root cell layers or increased number of cells in all tissues were reported (Benfey et al, 1993;Holding et al, 1994). Some arabidopsis mutants show altered morphological features of roots in response to external factors, for example nutrient availability (Hermans et al, 2010;Costa et al, 2011), exogenous auxin (Feng et al, 2012) and higher temperature (Baskin et al, 1992). A large group of temperature-sensitive mutants defective in the development of lateral and adventitious roots and, in some cases, of the primary root apex were isolated by a Japanese team (Konishi and Sugiyama, 2003;Sugiyama, 2003;Ohtani and Sugiyama, 2005;Ohtani et al, 2010;Otsuka and Sugiyama, 2012).…”

“…Overview of arabidopsis mutants that exhibit altered root morphology Radially swollen PR epidermal cell layer stp1 Decreased PR growth rate shr Short PR, ceased PR growth, large number of secondary roots at PR/hypocotyl junction, lack of meristematic and elongation zones, missing internal root cell layers Benfey et al, 1993 cob, lit, sab Expanded apical part of PR, abnormal root cell expansion in LR 1767 Shorter PR, reduced cellular elongation Holding et al, 1994 4792 Shorter radially expanded PR, swollen cells, increased number of cells in all tissues 5905 Shorter radially expanded PR, swollen cells in all tissues, reduced cellular elongation 7133 Swollen epidermal and cortical cells of PR 7203 Short PR, ceased PR growth, lack of endodermal cell layer, reduced RC Reduced LR number, failure in AR primordium initiation, PR development interrupted and aberrant LR morphology at higher temperature Konishi and Sugiyama, 2003; Ohtani and Sugiyama 2005; Ohtani et al, 2010 xpl Short PR, increased LR number, abnormal morphology of PR epidermal cells Cruz-Ramírez et al, 2004 puchi1 Retarded LR development, swollen LR proximal region Hirota et al, 2007 pin2,3,7 Increased LR density, fused LRs Laskowski et al, 2008 arm Increased LR number, reduced PR elongation, radial swelling on high nitrate Hermans et al, 2010 pdr23Short PR, reduced elongation zone in the absence of phosphorus, rapid loss of QC identity in the absence of nitrogenCosta et al, 2011 …”

miRNA778 and SUVH6 are involved in phosphate homeostasis in Arabidopsis

“…47 Although abundantly present in many soil types, most Pi is unavailable to plants [1]. To 48 acclimate to Pi-limited environments, plants have developed various strategies such as 49 enhancement of acquisition of Pi, coordination of Pi in different organs, and changes in root 50 structure and biochemical processes [2]. To dissect the mechanism for plant tolerance to Pi 51 limitation, great efforts have been made in identifying Pi-starvation responsive genes and 52 their networks [3][4][5].…”

“…We observed that Pi 431 deprivation led to the disappearance of starch grains in root tips of wild-type, while miR778-432 overexpression plants showed better organization of starch grains in the root tips. 433 It is presumed that a local Pi sensing mechanism exists in the primary roots, while the 434 lateral root development is governed by systemic Pi status [45,46,49]. A root system with 435 enhanced lateral root formation is considered as one of positive features in response to Pi 436 deficiency [3].…”

Soil Quality of Kapatagan Watershed, Lanao del Norte

“…Nitrogen and phosphorus are both part of biomolecules in plants but are the most limited in natural conditions. Nitrate is the most common form of nitrogen but is easily leached and denitrified; while orthophosphate for phosphorus, has low mobility and readily reacts with Ca +2 , Mg +2 and Al +3 , forming precipitates (Costa et al, 2011). All representative areas contained adequate concentration of potassium to support plant growth but varied nitrogen and phosphorus content.…”