Flowering pathway is regulated by bulb size in Lilium longiflorum (Easter lily)

Lilium longiflorum (Easter lily) vegetative propagation occurs through production of underground bulbs containing apical and axillary meristems. In addition, sexual reproduction is achieved by flowering of elongated shoots above the bulb. It is generally accepted that L. longiflorum has an obligatory requirement for vernalisation and that long day (LD) regime hastens flowering. However, the effect of bulb size and origin, with respect to axillary or apical meristems on flowering, as well as the interactions between these meristems are largely unknown. The aim of this study was to explore the effect of bulb size, vernalisation and photoperiod on L. longiflorum flowering. To this end, we applied vernalisation and photoperiod treatments to the different bulb sizes and used a system of constant ambient temperature of 25 °C, above vernalisation spectrum, to avoid cold-dependent floral induction during plant growth. Vernalisation and LD hasten flowering in all bulbs. Large, non-vernalised bulbs invariably remained at a vegetative stage. However, small non-vernalised bulbs flowered under LD conditions. These results demonstrate for the first time that cold exposure is not an obligatory prerequisite for L. longiflorum flowering, and that an alternative flowering pathway can bypass vernalisation in small bulbs. We suggest that apical dominance interactions determine the distinct flowering pathways of the apical and axillary meristems. Similar floral induction is achieved in propagated bulblets from scaling. These innovative findings in the field of geophyte floral induction represent valuable applicative knowledge for lily production.

Differential distributions of two adducin-like protein isoforms in the Drosophila ovary and early embryo

Adducin is a cytoskeletal protein that can function in vitro to bundle F-actin and to control the assembly of the F-actin/spectrin cytoskeletal network. The Drosophila Adducin-like (Add) locus (also referred to as hu-li tai shao (hts)) encodes a family of proteins of which several are homologous to mammalian adducin (Ding et al., Proc. Natl. Acad. Sci. USA 90, 2512-16, 1993; Yue & Spradling, Genes Dev. 6, 2443-54, 1992). We report the identification of two novel adducin isoforms: a 95 x 10(3) Mr form (ADD-95) and an 87 x 10(3) Mr form (ADD-87). We present a detailed analysis of the distribution patterns of ADD-95 and ADD-87 during oogenesis and embryogenesis. The isoforms are co-expressed in several cell- and tissue-types; however, only ADD-87 is present in mid- to late-stage oocytes. ADD-87 is present throughout the oocyte cortex at stages 9 and 10 of oogenesis but is detectable only at the anterior pole from stage 11 onward, correlated with localisation of Add-hts mRNA first to the cortex and then to the anterior pole of the oocyte. ADD-87 co-localises with F-actin and spectrin in the cortex of the oocyte through stage 10 of oogenesis, consistent with a possible role in cytoskeletal assembly or function predicted by mammalian studies.

Role of Adducin-like (hu-li tai shao) mRNA and protein localization in regulating cytoskeletal structure and function during Drosophila Oogenesis and early embryogenesis

Adducin is a cytoskeletal protein that can function in vitro to bundle F-actin and to control the assembly of the F-actin/spectrin cytoskeletal network. We previously reported cloning of the Drosophila Adducin-like (Add) locus [Ding et al., 1993] also referred to as hu-li tai shao (hts) [Yue and Spradling, 1992], and identification of two adducin-related protein isoforms: a 95 x 10(3) Mr form (ADD-95) and an 87 x 10(3) Mr form (ADD-87) [Zaccai and Lipshitz, 1996]. ADD-87 protein is present throughout the oocyte cortex at stages 9 and 10 of oogenesis but is restricted to its anterior pole from stage 11 onward. This ADD-87 protein localization is preceded by localization of Add-hts mRNA first to the cortex and then to the anterior pole of the oocyte. Mutation of the swallow gene results in delocalization of Add-hts mRNA and ADD-87 protein from the cortex of stage 9 and 10 oocytes, and from the anterior pole of later stage oocytes. Early embryos produced by swallow or Add-hts mutant females have severe defects in the distribution of F-actin and spectrin as well as abnormalities in nuclear division, nuclear migration, and cellularization. In addition to their cytoskeletal defects, embryos produced by swallow females have an abnormal anterior pattern because bicoid mRNA is delocalized from the anterior pole. In contrast, bicoid mRNA is still found at the anterior of embryos produced by Add-hts mothers. Thus swallow functions to restrict bicoid mRNA and Add-hts mRNA to the cortex of the oocyte. Cortical restriction of Add-hts mRNA and protein is required for the normal structure and function of the early embryonic F-actin/spectrin cytoskeleton. A defective embryonic cytoskeleton can be induced in either of two ways: (1) by delocalization of functional ADD from the oocyte cortex (as in swallow mutants), or (2) by reduction of ADD function while retaining its normal cortical localization during oogenesis (as in Add-hts mutants).

Paternal and maternal effects on grain weight and protein percentage in crosses between hexaploid and tetraploid high- and low-protein wheat genotypes

The inheritance of grain protein percentage and of grain weight were studied by crossing common and durum wheat cultivars with hexaploid and tetraploid breeding lines that excel in grain protein percentage. All high protein lines were descendants of the tetraploid wild emmer Triticum turgidum var. dicoccoides. One hexaploid cultivar was also crossed with a high-protein var. dicoccoides genotype. All crosses were made between low- and high-protein genotypes and were carried out reciprocally for any combination of genotypes; some of them between genotypes of the same ploidy level and some between hexaploid and tetraploid lines. Weight and protein percentage were determined in selfed and crossed grains that developed on the same spike. Mean weight and protein percentage were also determined in F2 grains of all crosses of the same ploidy level, either tetraploid or hexaploid. At any ploidy level, F1 grains resembled the selfed grains of the mother plant both in grain weight and in grain protein percentage, indicating a major maternal effect on both traits. F2 grains had similar grain weight to the heavy-grained parent, and their protein percentage was close to the midparents value. However, a slight indication of cytoplasmic inheritance of grain protein percentage was found in the comparison between most pairs of F2 reciprocals. The interspecific crosses (hexaploid with tetraploid combinations) yielded shrivelled seeds with highly reduced weight but relatively unchanged protein percentage. Weight reduction in the shrivelled hybrid grains (compared with the selfed ones) was more severe when the mother plant was hexaploid rather than tetraploid. The significance of the different tissues in determining grain weight and protein percentage is discussed.Key words: grain weight, grain protein percentage, maternal effect, paternal effect, reciprocal crosses, wheat, Triticum aestivum, Triticum turgidum var. dicoccoides.

The effect of substitution of chromosome 5S1 of Aegilops longissima for its wheat homoeologues on spike morphology and on several quantitative traits

Each pair of homoeologous group 5 chromosomes of common wheat (Triticum aestivum) cv. Chinese Spring was replaced by the homoeologous pair 5S1 of Aegilops longissima. The resulting substitution lines were selected by the isozyme markers SKDH or TPI-2 as well as by the presence of 21 bivalents at meiosis. In lines lacking 5B, the alien chromosome could not compensate for the missing Ph1 allele, as was evident by multivalent formation at meiosis and by reduced fertility. In the absence of 5A, chromosome 5S1 not only failed to compensate for the occurrence of spike speltoidy but enhanced its expression. Chromosome 5S1 had a moderate dosage effect on reducing plant height and promoting earliness. When added to the genome of common wheat, this chromosome induced a considerable increase in grain weight, but it could not compensate for the absence of a pair of any of its homoeologues. Other yield components were negatively affected in both addition and substitution lines, as well as in other aneuploids. Grain protein percentage of the different lines was negatively related to their yield per spike. This rendered difficult the evaluation of genes for grain protein percentage. The implication of the obtained results on the use of alien genes for wheat improvement is discussed.Key words: substitution lines, wheat, Triticum aestivum, Aegilops longissima, alien chromosomes, quantitative traits.