Research Note: Boron deficiency affects early infection events in the pea-Rhizobium symbiotic interaction

Abstract

The effects of the deprivation of boron (B) on Rhizobium–legume signaling and preinfection events have been investigated in pea (Pisum sativum L. cv. Argona). The capacity of root exudates to induce the activity of nodulation genes was modulated by B nutrition in the host plant. Exudates derived from B-deficient pea plants led to a low level of nod-gene expression that could be correlated with poor root hair curling. However, inoculation of B-deficient plants with bacteria grown in the presence of the nod-gene inducing hesperetin, restored root hair curling. The attachment of bacteria to roots was also diminished in plants grown in the absence of the micronutrient, and it was not recovered by hesperetin. Both phenomena provoked a reduction in nodulation of more than 50%. Furthermore, infection thread development was arrested at very early stages, and cell invasion by endocytosis was precluded, leading to almost empty of bacteria B-deficient nodules.