Determining the plasmotypic structure of rye populations by SCAR markers

In rye (Secale cereale L.), 2 types of cytoplasmic male sterility are known: Pampa type (CMS-P) and Vavilovii type (CMS-V). As an alternative method to the conventional plasmotype-genotype interaction test, for identification of the cytoplasm type, the use of sequence-characterised amplified region (SCAR) markers was validated in this study. In over 2600 individual rye plants, representing 26 populations originating from Poland (18 cultivars), Iran (5 populations of primitive rye), and South America (3 populations), the cytoplasm type was determined by using a set of 3 SCAR markers. For about 10% of these individuals, the plasmotype-genotype interaction test was performed in parallel. The results of both tests were fully consistent. In the majority of the Polish populations, CMS-V was present, and only 4 populations contained CMS-P. Primitive Iranian populations contained predominantly normal cytoplasm, and only occasionally CMS-P was identified in them. South American populations displayed a mixture of normal cytoplasm, CMS-P and CMS-V. This work validates the use of SCAR markers as a reliable and quick method to determine the plasmotypic diversity of rye populations on a large scale

Disruption of the pollen-expressed FERONIA homologs ANXUR1 and ANXUR2 triggers pollen tube discharge

The precise delivery of male to female gametes during reproduction in eukaryotes requires complex signal exchanges and a flawless communication between male and female tissues. In angiosperms, molecular mechanisms have recently been revealed that are crucial for the dialog between male (pollen tube) and female gametophytes required for successful sperm delivery. When pollen tubes reach the female gametophyte, they arrest growth, burst and discharge their sperm cells. These processes are under the control of the female gametophyte via the receptor-like serine-threonine kinase (RLK) FERONIA (FER). However, the male signaling components that control the sperm delivery remain elusive. Here, we show that ANXUR1 and ANXUR2 (ANX1, ANX2), which encode the closest homologs of the FER-RLK in Arabidopsis, are preferentially expressed in pollen. Moreover, ANX1-YFP and ANX2-YFP fusion proteins display polar localization to the plasma membrane at the tip of the pollen tube. Finally, genetic analyses demonstrate that ANX1 and ANX2 function redundantly to control the timing of pollen tube discharge as anx1 anx2 double-mutant pollen tubes cease their growth and burst in vitro and fail to reach the female gametophytes in vivo. We propose that ANX-RLKs constitutively inhibit pollen tube rupture and sperm discharge at the tip of growing pollen tubes to sustain their growth within maternal tissues until they reach the female gametophytes. Upon arrival, the female FER-dependent signaling cascade is activated to mediate pollen tube reception and fertilization, while male ANX-dependent signaling is deactivated, enabling the pollen tube to rupture and deliver its sperm cells to effect fertilization