Molecular analysis of the stylar‐expressed Solanum chacoense small asparagine‐rich protein family related to the HT modifier of gametophytic self‐incompatibility in Nicotiana

Abstract

SummaryGametophytic self-incompatibility (GSI) systems involving the expression of stylar ribonucleases have been described and extensively studied in many plant families including the Solanaceae, Rosaceae and Scrophulariaceae. Pollen recognition and rejection is governed in the style by specific ribonucleases called SRNases, but in many self-incompatibility (SI) systems, modifier loci that can modulate the SI response have been described at the genetic level. Here, we present at the molecular level, the isolation and characterization of two Solanum chacoense homologues of the Nicotiana HT modifier that had been previously shown to be necessary for the SI reaction to occur in N. alata (McClure et al., 1999). HT homologues from other solanaceous species have also been isolated and a phylogenetic analysis reveals that the HT genes fall into two groups. In S. chacoense, these small proteins named ScHT-A and ScHT-B are expressed in the style and are developmentally regulated during anthesis identically to the S-RNases as well as following compatible and incompatible pollination. To elucidate the precise role of each HT isoform, antisense ScHT-A and RNAi ScHT-B lines were generated. Conversion from SI to self-compatibility (SC) was only observed in RNAi ScHT-B lines with reduced levels of ScHT-B mRNA. These results confirm the role of the HT modifier in solanaceous SI and indicate that only the HT-B isoform is directly involved in SI.

The MIDASIN and NOTCHLESS genes are essential for female gametophyte development in Arabidopsis thaliana

“…The PCR fragment was first cloned in the sense orientation using the BamHI and KpnI sites of the silencing pDarth vector under the control of a double enhancer CaMV 35S promoter (O'Brien et al, 2002). To ensure specific RNAi targeting of the NLE gene, the abovementioned sequence used for RNAi was compared against the Arabidopsis transcript database (TAIR9).…”

NaStEP: A Proteinase Inhibitor Essential to Self-Incompatibility and a Positive Regulator of HT-B Stability inNicotiana alataPollen Tubes

“…Loss-of-function assays prove HT-B to be essential for pollen rejection in Nicotiana spp., Solanum spp., and Petunia spp. (McClure et al, 1999;Kondo et al, 2002;O'Brien et al, 2002;Sassa and Hirano, 2006;Puerta et al, 2009), although it is not expressed in SI Solanum habrochaites, prompting the speculation that in this species a related gene, HT-A, may function as a substitute (Covey et al, 2010). Immunolocalization shows that HT-B is readily taken up by pollen tubes during pollination.…”

Differential Activity of Four Selected Enzymes in the Pistils and Pollen Grains of Two Varieties of Hamelia Patens Jacq. (Rubiaceae) Following Compatible and Incompatible Pollination.

“…Self-incompatibility mechanism in angiosperms is widespread and has receivedconsiderable attention in recent years. Self-incompatibility genes have been identified,characterized, cloned and transferred to self-compatible lines in several species (Hoopen 1998 andBrien 2002). From the present study, it may be concluded that significant changes in the activities ofcertain key enzymes occur in the stigma and style tissues of Hamelia patens followingcompatible and incompatible pollination.…”