Low nitrogen availability inhibits the phosphorus starvation response in maize (Zea mays ssp. mays L.)

Abstract

Background Nitrogen (N) and phosphorus (P) are macronutrients essential for crop growth and productivity. In cultivated fields, N and P levels are rarely sufficient, contributing to the gap between realized and potential production. Fertilizer application increases nutrient availability, but is not available to all farmers, nor are current rates of application sustainable or environmentally desirable. Transcriptomic studies of cereal crops have revealed dramatic responses to either low N or low P single stress treatments. In the field, however, levels of both N and P may be suboptimal. The interaction between N and P starvation responses remains to be fully characterized. Results We characterized growth and root and leaf transcriptomes of young maize plants under nutrient replete, low N, low P or combined low NP conditions. We identified 1555 genes to respond to our nutrient treatments, in one or both tissues. A large group of genes, including many classical P starvation response genes, were regulated antagonistically between low N and P conditions. An additional experiment over a range of N availability indicated that a mild reduction in N levels was sufficient to repress the low P induction of P starvation genes. Although expression of P transporter genes was repressed under low N or low NP, we confirmed earlier reports of P hyper accumulation under N limitation. Conclusions Transcriptional responses to low N or P were distinct, with few genes responding in a similar way to the two single stress treatments. In combined NP stress, the low N response dominated, and the P starvation response was largely suppressed. A mild reduction in N availability was sufficient to repress the induction of P starvation associated genes. We conclude that activation of the transcriptional response to P starvation in maize is contingent on N availability.

The pho1;2a’-m1.1 allele of Phosphate1 conditions mis-regulation of the phosphorus starvation response in maize (Zea mays ssp. mays L.)

“…A previously reported increase in leaf P concentration under lowN (Schlüter et al, 2013;Torres-Rodríguez et al, 2021) was observed in all genotypes, further indicating that pho1;2a mutants are not compromised in the translocation of P from roots to leaves. Although we saw treatment effects on several elements, differences between genotypes were subtle, with limited statistical support that was not robust to correction for multiple testing (Supplemental Figure 3; Supplemental Data Set 1E).…”

“…Plants were grown under a greenhouse system as previously described (Torres-Rodríguez et al, 2021). Sand was used as substrate with nutrient conditions maintained by use of a (Hoagland and Broyer, 1936)).…”

“…Processed images were scaled and analyzed using GiA Roots software (Galkovskyi et al, 2012) as previously described (Torres-Rodríguez et al, 2021). After photography, the root system was divided into segments corresponding to increments of 15 cm depth (numbered 1 to 6) and segments weighed individually.…”

“…These strategies are modulated by plant P status and collectively referred to as the P starvation response (PSR). At the molecular level, P starvation promotes widespread change at both the transcriptional and post-transcriptional levels (Rausch and Bucher, 2002; Shin et al, 2004; Chang et al, 2019; Torres-Rodríguez et al, 2021). Physiological experiments have demonstrated that plants respond both locally to the Pi concentration of the environment and systemically to their internal Pi status (Thibaud et al, 2010; Lin W-Y et al, 2014).…”

Transcriptome-Wide Identification and Expression Profiling of SPX Domain-Containing Members in Responses to Phosphorus Deprivation of Pinus massoniana

“…Unveiling the molecular mechanism of plants' adaptation to phosphorus starvation would be pivotal for breeding phosphorus efficient species. In previous studies, the phosphorus starvation signaling pathway in plants has been well revealed, and more and more research has confirmed that SPX-domain proteins play a vital role in phosphorus homeostasis and signal transduction [8][9][10][11]. So far, the SPX members have been identified…”