NaTrxh is an essential protein for pollen rejection in Nicotiana by increasing S-RNase activity.

In self-incompatible Solanaceae, the pistil protein S-RNase contributes to S-specific pollen rejection in conspecific crosses, as well as to rejecting pollen from foreign species or whole clades. However, S-RNase alone is not sufficient for either type of pollen rejection. We describe a thioredoxin (Trx) type h from Nicotiana alata, NaTrxh, which interacts with and reduces S-RNase in vitro.

Mutations in two pollen self-incompatibility factors in geographically marginal populations of Solanum habrochaites impact mating system transitions and reproductive isolation.

Premise Of The Study: Self-incompatibility (SI) is a mechanism that prevents inbreeding in many plant species. The mutational breakdown of SI occurs frequently, yet relatively little is known about the evolutionary steps involved in the progressive loss of pistil and pollen SI function.

Methods: In Solanaceae, SI is the S-RNase-based gametophytic type.

Restoring pistil-side self-incompatibility factors recapitulates an interspecific reproductive barrier between tomato species.

Interspecific reproductive barriers are poorly understood, but are central to the biological species concept. The pre-zygotic barriers between red- and green-fruited species in the tomato clade of the genus Solanum provide a model to better understand these barriers in plants. Compatibility usually follows the SI x SC rule: pollen from self-compatible (SC) red-fruited species is rejected on pistils of the predominantly self-incompatible (SI) green-fruited species, but the reciprocal crosses are compatible.

Multiple features that distinguish unilateral incongruity and self-incompatibility in the tomato clade.

Wild tomato species in Solanum Section Lycopersicon often exhibit two types of reproductive barriers: self-incompatibility (SI) and unilateral incompatibility or incongruity (UI), wherein the success of an inter-specific cross depends on the direction of the cross. UI pollen rejection often follows the 'SI × SC' rule, i.e.

Gametophytic self-incompatibility: understanding the cellular mechanisms involved in "self" pollen tube inhibition.

Self-incompatibility (SI) prevents the production of "self" seed and inbreeding by providing a recognition and rejection system for "self," or genetically identical, pollen. Studies of gametophytic SI (GSI) species at a molecular level have identified two completely different S-genes and SI mechanisms. One GSI mechanism, which is found in the Solanaceae, Rosaceae and Scrophulariaceae, has S-RNase as the pistil S-component and an F-box protein as the pollen S-component.

The stylar 120 kDa glycoprotein is required for S-specific pollen rejection in Nicotiana.

S-RNase participates in at least three mechanisms of pollen rejection. It functions in S-specific pollen rejection (self-incompatibility) and in at least two distinct interspecific mechanisms of pollen rejection in Nicotiana. S-specific pollen rejection and rejection of pollen from Nicotiana plumbaginifolia also require additional stylar proteins.