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A novel anther-specific chalcone synthase-like gene, TaCHSL1, was isolated and characterized. The TaCHSL1 transcript was detected only within the tapetum during the "free" and early vacuolated microspore stages in both wheat and triticale. Sequence analysis indicated that the 41.8 kDa TaCHSL1 deduced protein belongs to a small distinct group of type III polyketide synthases that includes angiosperm and gymnosperm orthologs shown to be anther-specific. TaCHSL1 sequence characteristics and conservation, as well as its restricted expression pattern, point to a distinct and important biochemical role in developing anthers.

The isolation, characterization and regulation of expression of a maize silk-specific gene is described. zmgrp5 (Zea mays glycine-rich protein 5) encodes a 187 amino acid glycine-rich protein that displays developmentally regulated silk-specific expression. Northern, Western, in situ mRNA hybridization and transient gene expression analyses indicate that zmgrp5 is expressed in silk hair and in cells of the vascular bundle and pollen tube transmitting tissue elements. The protein is secreted into the extracellular matrix and is localized in the cell wall fraction mainly through interactions mediated by covalent disulphide bridges. Taken together, these results suggest that the protein may play a role in maintaining silk structure during development. This is the first documented isolation of a stigma-specific gene from maize, an important agronomic member of the Poaceae family.

We have previously isolated a CCAAT-binding factor B subunit gene ( BnCBF-B) from Brassica napus that is widely expressed in different plant tissues and whose role is still unknown. To investigate the importance of this transcription factor subunit in plant reproductive tissues, we targeted antisense BnCBF-B transcripts to the tapetum of transgenic B. napus plants. Of the 24 independent transformants, 13 yielded reduced quantities of viable pollen, of which five were unable to produce the elongated siliques indicative of normal seed set. The decrease in pollen viability probably resulted from the precocious degeneration of the tapetal cell layer observed in these plants. Surprisingly, the male-sterile phenotype was also accompanied by a decrease in female fertility, which could be due to the expression of the antisense BnCBF-B transcripts in the female reproductive structures of the transgenic plants. These results suggest that the BnCBF-B gene plays a critical non-redundant role in plant reproductive tissues.

Eighteen of 20 short-season soybean (Glycine max (L.) Merrill) genotypes (maturity group 0 and 00) screened for proliferative embryogenic capacity formed secondary globular embryos, at rates of 1-70% of cultured immature cotyledons. Five genotypes produced embryogenic cultures which were proliferative for at least 6 months. Proliferative embryogenic cultures of AC Colibri and X2650-7-2-3 were bombarded using a Bio-Rad PDS-1000/He particle gun. Co-bombardments with plasmid pairs pHygr (encoding a type IV aminoglycoside phosphotransferase;aphIV) and pRD300pat (encoding a phosphinothricin N-acetyltransferase;pat) or pRD300pat and pFF19G (β-glucuronidase;uidA or gus) resulted, respectively, in 12 hygromycin-selected lines with multiple insertions of aphIV and pat, and two l-phosphinothricin-selected lines plus three β-glucuronidase-positive lines recovered without selection. Although fertile plants were recovered from young proliferative cultures, transgenic plants, which were derived from cultures 12-14 months of age, were sterile.

Short-season adapted soybean [Glycine max (L.) Merrill] genotypes (maturity group 0 and 00) were susceptible to Agrobacterium tumefaciens in tumor-formation assays with A. tumefaciens strains A281, C58 and ACH5. The response was bacterial-strain and plant-cultivar dependent. In vitro Agrobacterium-mediated transformation of cotyledonary node explants of these genotypes with A. tumefaciens EHA105/pBI121 was inefficient but resulted in a transgenic AC Colibri plant carrying a linked insertion of the neomycin phosphotransferase and β-glucuronidase (gus) transgenes. The transgenes were transmitted to the progeny and stable gus expression was detected in the T 7 generation. The low rate of recovery of transgenic plants from the co-cultured cotyledonary explants was attributed to inefficient transformation of regenerable cells, and/or poor selection or survival of such cells and not to poor susceptibility to Agrobacterium, since, depending on the cultivar, explants were transformed at a rate of 27-92%, but transformation events were usually restricted to non-regenerable callus.

A 647-bp 5'-flanking fragment obtained from genomic clone Sta 44G(2) belonging to a family of polygalacturonase genes expressed inBrassica napus pollen was fused to theβ-glucuronidase (GUS) marker gene. This fusion construct was introduced intoB. napus plants viaAgrobacterium tumefaciens transformation. Analysis of the transgenicB. napus plants revealed that this promoter fragment is sufficient to direct GUS expression specifically in the anther and that GUS activity increases in pollen during maturation.