Characterization of root response to phosphorus supply from morphology to gene analysis in field-grown wheat

Abstract

The adaptations of root morphology, physiology, and biochemistry to phosphorus supply have been characterized intensively. However, characterizing these adaptations at molecular level is largely neglected under field conditions. Here, two consecutive field experiments were carried out to investigate the agronomic traits and root traits of wheat (Triticum aestivum L.) at six P-fertilizer rates. Root samples were collected at flowering to investigate root dry weight, root length density, arbusular-mycorrhizal colonization rate, acid phosphatase activity in rhizosphere soil, and expression levels of genes encoding phosphate transporter, phosphatase, ribonucleases, and expansin. These root traits exhibited inducible, inhibitory, or combined responses to P deficiency, and the change point for responses to P supply was at or near the optimal P supply for maximum grain yield. This research improves the understanding of mechanisms of plant adaptation to soil P in intensive agriculture and provides useful information for optimizing P management based on the interactions between soil P dynamics and root processes.

Efficient Mineral Nutrition: Genetic Improvement of Phosphate Uptake and Use Efficiency in Crops

“…However, enhanced induction of TaPht1 transcripts might be either a short-term adaptation to local P depletion or unevenly distributed patterns of P availability. High persistent induction during severe long-term scarcity as an adaptation mechanism seems questionable and should be investigated on field-grown crops as performed by Teng et al (2013). Enhancing P acquisition by over-expressing phosphate transporter genes has been reported in tobacco cell cultures (Mitsukawa et al 1997) but could not be confirmed at the plant level (Rae et al 2004).…”

“…A potential candidate target would be characterised by being a key factor in the molecular mechanism of the P starvation response, adaptation and genetic diversity responsible for low P tolerance, keeping in mind that there is a need for different strategies in low-input and high-input systems, focusing more on PAE or PUE respectively. Teng et al (2013) investigated the expression profiling of known P starvation-induced genes in wheat under different levels of P fertiliser and soil Olsen P, proving that the turning point for the genetic response was the critical P level. This observation leads to a more general model (Fig.…”

“…4.3 Model for of the optimal yield (red up arrow) coinciding with the induction of P-starvation marker genes (green down arrow) in field-derived wheat roots shifting towards lower soil Olsen-P levels with improved P efficiency traits (Teng et al 2013) et al 2009;Yao et al 2011) exposed to a short-term P starvation period; particularly transcriptome, proteome or metabolite profiling studies (Wang et al 2002;Wasaki et al 2003;Hammond et al 2004;Calderón-Vázquez et al 2008;Huang et al 2008;Oono et al 2011;Liang et al 2010;Oono et al 2013). Even if these profiling studies provided a useful tool to study the response mechanisms with regards to adaptation to nutrient stresses (Hammond et al 2004;Nilsson et al 2010), the majority used hydroponically grown plant material exposed to short-term P starvation.…”

“…A strong induction of Pht1 transporters was reported in the majority of transcript profiling studies where plants were exposed to a short-term P starvation period and grown mainly in nutrient solution (Wang et al 2002;Wasaki et al 2003;Calderón-Vázquez et al 2008;Huang et al 2008;2011) and in the field (Teng et al 2013), which makes them obvious targets for genetic improvement. However, enhanced induction of TaPht1 transcripts might be either a short-term adaptation to local P depletion or unevenly distributed patterns of P availability.…”

“…However, the lack of complete genome sequence information has hindered detailed investigation in wheat. Pht1 transporters, which are preferentially or exclusively expressed in roots, were found in barley (Smith et al 1999;Rae et al 2003), wheat (Davies et al 2002;Teng et al 2013;Wang et al 2013), Arabidopsis (Mudge et al 2002;Muchhal et al 1996), rice (Paszkowski et al 2002) maize (Nagy et al 2006) and tomato (Liu et al 1998;Muchhal and Raghothama 1999). Furthermore, Pht1 expression in shoot tissues has been reported e.g.…”