Male-sterile mutation alters Zea m 1 (β-expansin 1) accumulation in a maize mutant

gaMS-2 is a gametophytic male-sterile mutant of maize, with sterile pollen grains developmentally blocked at the binucleate stage. To characterise differentially expressed proteins in gaMS-2 pollen, we compared protein profiles of anthers and mature pollen from heterozygous GaMS-2/gaMS-2 plants and wild type (wt) plants by two-dimensional electrophoresis (2-DE). A basic protein present at a greatly reduced level in GaMS-2/gaMS-2 anthers was subsequently identified by tandem mass spectrometry as Zea m 1 (a glycoprotein of 31 kDa), the major group-1 allergen of maize pollen and a member of the β-expansin 1 family. Moreover, we show that Zea m 1 can be deglycosylated by peptide N-glycosidase F. After deglycosylation, four major isoforms-Zea m 1a (more acetic), Zea m 1b, Zea m1c and Zea mid (more basic) - can be discriminated in wt anther in 2-DE immunoblots probed with a monoclonal antibody against the group-1 pollen allergen, whereas all the isoforms, especially Zea m 1a, exist at reduced levels in GaMS-2/gaMS-2 anthers. Furthermore, the reduced Zea m 1 accumulation in the mutant appears to occur in immature pollen but not in anther sporophytic tissues. Finally, we separated sterile pollen grains (at the mononucleate stage) from fertile ones using 42% Percoll solution, and found that Zea m 1 is barely detectable in sterile pollen grains. Together, our results indicate that a reduced Zea m 1 level is associated with the sterile phenotype of gaMS-2. © Springer-Verlag 2004

A DEF/GLO-like MADS-box gene from a gymnosperm: Pinus radiata contains an ortholog of angiosperm B class floral homeotic genes

Many double-flowered plants, in which petals replace stamens, are highly valued by the horticultural industry. These mutants exhibit a homeotic conversion of floral organs and frequently also a meristic increase n floral organ number. By gamma irradiation we generated a novel double-flowered mutant, Sl-dfl, in a male genetic background of the dioecious plant white campion (Silene latifolia). This mutant shows a homeotic conversion of stamens to petals, together with uncontrolled growth and division of second and third whorl floral organ primordia, causing a proliferation of petal and chimeric petal-stamen organs. We characterize this mutant developmentally by scanning electron microscopy and demonstrate that the effects of the mutation commence following the formation of a correctly partitioned floral meristem with a wild-type arrangement of organ primordia. We have commenced a molecular investigation of the Sl-dfl mutant by testing the expression and genomic organization of the known white campion putative MADS-box floral homeotic genes. These studies indicate four MADS-box genes to be unlikely to be mutated in the double-flowered mutant. The possibility that a putative C- function MADS-box gene may cause the mutant phenotype has not currently been excluded, though our morphological studies suggest that a C-function mutation is not involved in this case. We conclude that a number of different classes of double-flowered mutation exist, not all of which are currently known from model plant species. This may be indicative of important developmental differences between species and may also emphasize a need for comparative studies of floral development

Detection of genetic factors controlling pollen-style interaction in maize

n order to detect loci specifically related to pollen-style interaction in maize, linkage analysis to RFLP markers was performed on a population of recombinant inbred lines, the pollen of which was used to pollinate female plants of two different genotypes: the F-1 from which the recombinant inbred population was derived ('self female') and a genetically unrelated hybrid genotype ('cross female'). Besides pollen grain germinability and pollen tube growth rate on the two females, pollen general competitive ability and pollen specific competitive ability for both traits were evaluated, following the procedure used to estimate general and specific combining ability, applied to the pollen-style genetic combination instead of to the hybrid genetic combination. A clear advantage of recombinant inbred line pollen, in terms of germination and early growth, was revealed on self female tissues whereas an inverse effect was detected for tube growth rate: tube growth, until fertilization, was faster on the female of unrelated genotype. Linkage analysis to molecular markers (RFLP) of germinability and of tube growth rate on the two stylar genotypes identified nine QTLs for the first trait on the self and eight on the cross female; four chromosome regions for tube growth rate were detected on the self and 11 on the cross style. Most of the general competitive ability effects were localized in the regions where QTLs for germinability or pollen tube growth were detected, in particular on the cross female; on the contrary, most of the loci for pollen specific competitive ability effects proved to be localized in different chromosome regions