There are differences in the microRNA 399-Mediated PvPHO2 Regulation within the PvPHR1 Signaling Pathway between two common bean genotypes that respond differently to phosphorus deficiency.

• AA Ferreira

  English

  Author

Low phosphate (P) in the soil often limits crop yield of the significant legume, the common
bean (Phaseolus vulgaris). The common bean's BAT477 and DOR364 genotypes react differently to P
shortage. Under P deprivation, plants with the BAT477 P shortage tolerant genotype displayed more
phosphate content and root biomass than DOR364 plants. An important part of the reaction to P shortage
is the PvPHR1 transcription factor-signaling pathway. The target gene of PvmiR399 is PvPHO2, a
negative regulator of this pathway that produces a ubiquitin E2 conjugase that facilitates the breakdown
of P-responsive proteins. When P is lacking, PvPHO2 is downregulated in BAT477 plants, but this
reaction is not seen in P-starved DOR364 plants. In the 5' UTR region of both genotypes, five potential
PvmiR399 binding sites were found. The fifth location (the binding site of PvPHO2) had three base
alterations and greater complementarity scores in DOR364 compared to BAT477, but the other four sites
displayed the same DNA sequence. Modified 5'RACE tests showed that DOR364 P-starved plants have
altered PvmiR399 binding and/or processing. We suggest that the DOR364 genotype would have a
stronger PvPHO2-mediated degradation of P-responsive proteins with less P deficit tolerance due to a less
effective cleavage of the PvPHO2 mRNA mediated by PvmiR399 itself.

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