Identification of vacuolar phosphate influx transporters in Brassica napus

Abstract

Recent progress has shown that vacuolar Pi transporters (VPTs) are important for cellular Pi homoeostasis in Arabidopsis thaliana and Oryza sativa under fluctuating external Pi supply, but the identity and involvement of VPTs in cellular Pi homoeostasis in Brassica napus is poorly understood. Here, we identified two vacuolar Pi influx transporters B. napus, BnA09PHT5;1b and BnCnPHT5;1b, and uncovered their necessity for cellular Pi homoeostasis through functional analysis. Both Brassica proteins are homologs of Arabidopsis AtPHT5;1 with a similar sequence, structure, tonoplast localization, and VPT activity. Brassica pht5;1b double mutants had smaller shoots and larger shoot cellular Pi concentrations than wild-type B. napus, which contrasts with a previous study of the Arabidopsis pht5;1 mutant, suggesting that PHT5;1-VPTs play different roles in cellular Pi homoeostasis in seedlings of B. napus and A. thaliana. Disruption of BnPHT5;1b genes also caused Pi toxicity in floral organs, reduced seed yield and impacted seed traits, consistent with the proposed role of AtPHT5;1 in floral Pi homoeostasis in Arabidopsis. Taken together, our studies identified two vacuolar Pi influx transporters in B. napus and revealed the distinct and conserved roles of BnPHT5;1bs in cellular Pi homoeostasis in this plant species.

VPT‐like genes modulate Rhizobium–legume symbiosis and phosphorus adaptation

“…Nevertheless, results showed that the cytosolic Pi levels of nodule tissues were lower in mtvpt2 and mtvpt3 under both high and low phosphate conditions, especially under low phosphate stress (Figure 8). These findings indicate that the decrease in the nodule number of mtvpt2 and mtvpt3 under high phosphate conditions was caused by an insufficient supply of cytosolic Pi and not phosphate toxicity as in the case of vpts and bnpht5;1b (Han et al., 2022; Liu et al., 2015; Luan et al., 2019). A steady stream of phosphate can be imported into nodules under high phosphate conditions.…”

“…Although MtVPT2 and MtVPT3 have similar effects on plant phosphorus adaptive growth phenotypes, they have different underlying mechanisms. MtVPT3 expression is similar to VPT1 expression in A. thaliana and BnPHT5;1b expression in Brassica napus , which is mainly induced by high phosphate levels (Liu et al., 2015; Han et al., 2022). Similar to VPT1 , MtVPT3 expression is also mainly induced by high phosphate in older leaves but not in young leaves (Figure 5b).…”

“…Previous studies showed that VPT (Pht5) family proteins regulate plant phosphorus adaptation by regulating vacuolar Pi storage (Han et al., 2022; Liu et al., 2015; Liu, Huang, et al., 2016). In this study, results showed that VPT ‐like genes ( MtVPT2 and MtVPT3) are involved in phosphorus adaptation in M. truncatula , a legume plant.…”

“…Unlike the A. thaliana vpt1 mutant, which had lower Pi levels in both the shoot and in the root, mtvpt3 mutant had higher Pi levels in the shoot than the wild type, suggesting that MtVPT3 may not be the major gene responsible for vacuolar Pi storage in the shoot of M. truncatula (Liu et al., 2015). Similarly, BnPHT5;1b mutation can increase the phosphate concentration of shoot in Brassica napus (Han et al., 2022). However, it is not clear whether BnPHT5;1b can also show a tolerant phenotype under low phosphate conditions.…”

Sustainable Cannabis Nutrition: Elevated root-zone phosphorus significantly increases leachate P and does not improve yield or quality

“…P toxicity is uncommon in crop plants, and there is variability in susceptibility among plant taxa ( Lambers, 2022 ). P toxicity is typically caused by high root-zone P and an inability to regulate P transport at the root surface or store excess cytosolic P in vacuole ( Han et al., 2022 ). Cannabis appears to tolerate elevated P without detrimental effects, but this is not a reason to over fertilize.…”