The regulatory module BnamiR827-BnaA09.NLA1-BnaPHT1s modulates phosphate homeostasis, pollen viability and seed yield in Brassica napus.

Phosphorus (P) is an essential macronutrient for the growth and yield of crops. However, there is limited understanding of the regulatory mechanisms of phosphate (Pi) homeostasis, and its impact on growth, development, and yield-related traits in Brassica napus. Here, we identified four NITROGEN LIMITATION ADAPATATION1 (BnaNLA1) genes in B. napus, their expression was predominant in roots and suppressed by Pi starvation-induced MicroRNA827s (BnamiR827s). All the BnaNLA1 proteins have similar sequences, subcellular localizations, and abilities to rescue the growth defects of atnla1 mutant. One of the genes, BnaA09.NLA1 expressed abundantly in roots, and also in old leaves, anthers and pollens. Knocking out of BnaNLA1(s) or overexpressing BnamiR827 resulted in increased concentrations of Pi in leaves as well as in stamen and had reduced pollen viability thereby negatively impacting seed yield. BiFC and split-ubiquitin Y2H analyses demonstrated that BnaA09.NLA1 interacted with seven Pi transporters highly expressed in roots and/or anthers (i.e., BnaPT8/10/11/27/35/37/42) to regulate Pi uptake and Pi allocation in anthers. Taken together, this study demonstrates that the BnamiR827-BnaA09.NLA1-BnaPHT1s module is involved in regulating Pi uptake and Pi allocation in floral organs, which is vital for the growth, pollen viability and seed yield of B. napus.