Environmental heterogeneity influences the reliability of secondary sexual traits as condition indicators.

Numerous studies have shown positive associations between ornaments and condition, as predicted by indicator models of sexual selection. However, this idea is continuously challenged by opposite results, which reveal our lack of full understanding of how sexual selection works. Environmental heterogeneity may explain such inconsistencies, but valid field tests of this idea are currently lacking. We first analysed the relationship between condition and ornament expression from nine populations over 7 years in a wild bird, the red grouse Lagopus lagopus scoticus. We then manipulated male aggressiveness at the population level by means of testosterone implants in a replicated field experiment. We found that the relationship between condition and ornamentation varied greatly between environments and became stronger when environmental conditions (ECs) were worse or when aggressiveness in the population was experimentally increased. Some ornaments may therefore reliably advertise a better condition only in adverse ECs. Considering environmental heterogeneity can help reconcile conflicting findings regarding the reliability of ornaments as indicators of condition and will help our understanding of sexual selection processes.

The effect of aggressiveness on the population dynamics of a territorial bird.

A central issue in ecology lies in identifying the importance of resources, natural enemies and behaviour in the regulation of animal populations. Much of the debate on this subject has focused on animals that show cyclic fluctuations in abundance. However, there is still disagreement about the role of extrinsic (food, parasites or predators) and intrinsic (behaviour) factors in causing cycles. Recent studies have examined the impact of natural enemies, although spatial patterns resulting from restricted dispersal or recruitment are increasingly recognized as having the potential to influence unstable population dynamics. We tested the hypothesis that population cycles in a territorial bird, red grouse Lagopus lagopus scoticus, are caused by delayed density-dependent changes in the aggressiveness and spacing behaviour of males. Here we show that increasing aggressiveness experimentally for a short period in autumn reduced recruitment and subsequent breeding density by 50%, and changed population trajectories from increasing to declining. Intrinsic processes can therefore have fundamental effects on population dynamics.

The specificity of polygalacturonase-inhibiting protein (PGIP): a single amino acid substitution in the solvent-exposed beta-strand/beta-turn region of the leucine-rich repeats (LRRs) confers a new recognition capability.

Two members of the pgip gene family (pgip-1 and pgip-2) of Phaseolus vulgaris L. were expressed separately in Nicotiana benthamiana and the ligand specificity of their products was analysed by surface plasmon resonance (SPR). Polygalacturonase-inhibiting protein-1 (PGIP-1) was unable to interact with PG from Fusarium moniliforme and interacted with PG from Aspergillus niger; PGIP-2 interacted with both PGs. Only eight amino acid variations distinguish the two proteins: five of them are confined within the beta-sheet/beta-turn structure and two of them are contiguous to this region. By site-directed mutagenesis, each of the variant amino acids of PGIP-2 was replaced with the corresponding amino acid of PGIP-1, in a loss-of-function approach. The mutated PGIP-2s were expressed individually in N.benthamiana, purified and subjected to SPR analysis. Each single mutation caused a decrease in affinity for PG from F.moniliforme; residue Q253 made a major contribution, and its replacement with a lysine led to a dramatic reduction in the binding energy of the complex. Conversely, in a gain-of-function approach, amino acid K253 of PGIP-1 was mutated into the corresponding amino acid of PGIP-2, a glutamine. With this single mutation, PGIP-1 acquired the ability to interact with F.moniliforme PG.

The promoter of a gene encoding a polygalacturonase-inhibiting protein of Phaseolus vulgaris L. is activated by wounding but not by elicitors or pathogen infection.

Polygalacturonase-inhibiting proteins (PGIPs), leucine-rich repeat (LRR) proteins evolutionarily related to several plant resistance genes, bind to and regulate the action of fungal endopolygalacturonases. In Phaseolus vulgaris L., PGIPs are encoded by a gene family comprising at least five members. As a start for a systematic analysis of the regulation of the pgip family, we have analysed the ability of the promoter of the bean gene pgip-1 to direct expression of beta-glucuronidase (GUS) in transfected tobacco protoplasts, microbombarded bean and tobacco leaves, and transgenic tobacco plants. In protoplasts, the pgip-1 gene region from nucleotide (nt) -2004 to nt +27 directed a level of expression that was as high as that directed by the cauliflower mosaic virus (CaMV) 35S promoter and could not be further induced by elicitor treatment; alteration of the region immediately following the TATAA sequence at nt -29 abolished expression. Upon stable integration into tobacco plants of the pgip-1 promoter-GUS construct, as well as of a -394 deletion, expression was detected for both constructs mainly in the stigma and, to a lesser extent, in the anthers and in the conductive vascular tissue. The promoter responded to wounding but not to oligogalacturonides, fungal glucan, salicylic acid, cryptogein, or pathogen infection. This expression pattern does not mirror that of the whole pgip gene family.

Polygalacturonase-inhibiting proteins (PGIPs) with different specificities are expressed in Phaseolus vulgaris.

The pgip-1 gene of Phaseolus vulgaris, encoding a polygalacturonase-inhibiting protein (PGIP), PGIP-1 (P. Toubart, A. Desiderio, G. Salvi, F. Cervone, L. Daroda, G. De Lorenzo, C. Bergmann, A. G. Darvill, and P. Albersheim, Plant J. 2:367-373, 1992), was expressed under control of the cauliflower mosaic virus 35S promoter in tomato plants via Agrobacterium tumefaciens-mediated transformation. Transgenic tomato plants with different expression levels of PGIP-1 were used in infection experiments with the pathogenic fungi Fusarium oxysporum f. sp. lycopersici, Botrytis cinerea, and Alternaria solani. No evident enhanced resistance, compared with the resistance of untransformed plants, was observed. The pgip-1 gene was also transiently expressed in Nicotiana benthamiana with potato virus X (PVX) as a vector. PGIP-1 purified from transgenic tomatoes and PGIP-1 in crude protein extracts of PVX-infected N. benthamiana plants were tested with several fungal polygalacturonases (PGs). PGIP-1 from both plant sources exhibited a specificity different from that of PGIP purified from P. vulgaris (bulk bean PGIP). Notably, PGIP-1 was unable to interact with a homogeneous PG from Fusarium moniliforme, as determined by surface plasmon resonance analysis, while the bulk bean PGIP interacted with and inhibited this enzyme. Moreover, PGIP-1 expressed in tomato and N. benthamiana had only a limited capacity to inhibit crude PG preparations from F. oxysporum f. sp. lycopersici, B. cinerea, and A. solani. Differential affinity chromatography was used to separate PGIP proteins present in P. vulgaris extracts. A PGIP-A with specificity similar to that of PGIP-1 was separated from a PGIP-B able to interact with both Aspergillus niger and F. moniliforme PGs. Our data show that PGIPs with different specificities are expressed in P. vulgaris and that the high-level expression of one member (pgip-1) of the PGIP gene family in transgenic plants is not sufficient to confer general, enhanced resistance to fungi.

An investigation into the role of initial K(L)a on the growth and alkaloid accumulation by cultures of Catharanthus roseus.

The effect of initial K(L)a on the batch culture of Catharanthus roseus ID1 in a 12.5-L bioreactor has been examined. Optimum K(L)a values were found for both growth and alkaloid accumulation. Different sparger designs were used to alter the K(L)a values. High K(L)a values caused increased aggregation of the cultures, depressed biomass yields, and altered patterns of alkaloid accumulation.