Thepho1;2a′‐m1.1allele ofPhosphate1conditions misregulation of the phosphorus starvation response in maize (Zea maysssp.maysL.)

Abstract

Plant PHO1 proteins play a central role in the translocation and sensing of inorganic phosphate. The maize (Zea mays ssp. mays) genome encodes two co-orthologs of the Arabidopsis PHO1 gene, designated ZmPho1;2a and ZmPho1;2b. Here, we report the characterization of the transposon footprint allele Zmpho1;2a 0 -m1.1, which we refer to hereafter as pho1;2a. The pho1;2a allele is a stable derivative formed by excision of an Activator transposable element from the ZmPho1;2a gene. The pho1;2a allele contains an 8-bp insertion at the point of transposon excision that disrupts the reading frame and is predicted to generate a premature translational stop. We show that the pho1;2a allele is linked to a dosage-dependent reduction in Pho1;2a transcript accumulation and a mild reduction in seedling growth. Characterization of shoot and root transcriptomes under full nutrient, low nitrogen, low phosphorus, and combined low nitrogen and low phosphorus conditions identified 1100 differentially expressed genes between wild-type plants and plants carrying the pho1;2a mutation. Of these 1100 genes, 966 were upregulated in plants carrying pho1;2a, indicating the wildtype PHO1;2a to predominantly impact negative gene regulation. Gene set enrichment analysis of the pho1;2a-misregulated genes revealed associations with phytohormone signaling and the phosphate starvation response. In roots, differential expression was broadly consistent across all nutrient conditions. In leaves, differential expression was largely specific to low phosphorus and combined low nitrogen and low phosphorus conditions. Of 276 genes upregulated in the leaves of pho1;2a mutants in the low phosphorus condition, 153 were themselves induced in wild-type plants with respect to the full nutrient condition. Our observations suggest that Pho1;2a functions in the fine-tuning of the transcriptional response to phosphate starvation through maintenance and/or sensing of plant phosphate status.

Central Roles of ZmNAC128 and ZmNAC130 in Nutrient Uptake and Storage during Maize Grain Filling

“…To date, four sugar transporters ( ZmSWEET4c [sugars will eventually be exported transporter 4c] [ 3 ], ZmSUGCAR1 [sucrose and glucose carrier 1] [ 4 ], ZmSUT1 [sucrose transporter 1] [ 5 ], ZmSUT7 [ 6 ]) and one cell wall invertase-encoding gene ( ZmMN1 [miniature 1]) [ 7 ], in the BETL, have been shown to function in the uptake of carbohydrates/carbons (C). Recently, duplicate maize PHO1-type phosphate (P) transporters, ZmPHO1;2a and ZmPHO1;2b have been shown to function in P reallocation and grain filling [ 8 , 9 ]. Additionally, the Zn-NA (nicotianamine) transporter gene ZmYSL2 has been found to be involved in the zinc (Zn) upload to maize kernels [ 10 ].…”