Reduced expression ofmajor royal jelly protein 1gene in the mushroom bodies of worker honeybees with reduced learning ability

Abstract

Reduced expression of major royal jelly protein 1 gene in the mushroom bodies of worker honeybees with reduced learning ability. Apidologie, Springer Verlag, 2010, 41 (2), Abstract -The learning ability of European honeybees, Apis mellifera, develops with age. However, when worker bees are isolated from their colony and are fed only sucrose solution, their learning development is hindered. This rearing method has allowed us to compare worker bees of the same age but with different learning abilities. In this study, we examined the influence of this rearing condition on gene expression in the mushroom body, which is the insect brain center involved in learning and memory. A differential display experiment comparing worker bees maintained in a hive with those reared in isolation showed that the expression of the major royal jelly protein (mrjp) 1 gene was reduced in the isolated worker bees. MRJP1 is synthesized in the hypopharyngeal gland and serves a nutritional function in larval and queen food. Our results suggest that mrjp1 is also important in brain function, possibly involved in the development of learning ability.Apis mellifera / mrjp / gene expression / differential display / social environment Corresponding author: M. Hojo, hojoj@tmu.ac.jp Present address:

Origin and function of the major royal jelly proteins of the honeybee (Apis mellifera) as members of the yellow gene family

“…Kucharski et al (1998) reported mrjp1 expression in the Kenyon cells of the mushroom bodies in the honeybee brain, a new, then unknown function for MRJPs. The expression of mrjp1 in the mushroom bodies was higher in worker bees sampled from colonies compared to isolated ones (Hojo et al, 2010), that are known to have a decreased learning ability (Ichikawa & Sasaki, 2003). MRJP1 was found to be up-regulated in nurses compared to queens, foragers or drones and to be located in the antennal lobe, optical lobe and mushroom bodies Peixoto et al, 2009).…”

“…In addition, workers in colonies where the queen is lost activate their ovaries to produce eggs and synthesize MRJP1 and 2 in their glands like normal nurse bees (Nakaoka, Takeuchi & Kubo, 2008). Since then, the expression of mrjp1-8 in the brain has been shown repeatedly (Whitfield et al, 2002;Thompson et al, 2006;Garcia et al, 2009;Peixoto et al, 2009;Hojo et al, 2010). Kucharski et al (1998) reported mrjp1 expression in the Kenyon cells of the mushroom bodies in the honeybee brain, a new, then unknown function for MRJPs.…”

“…Since then, the expression of mrjp1-8 in the brain has been shown repeatedly (Whitfield et al, 2002;Thompson et al, 2006;Garcia et al, 2009;Peixoto et al, 2009;Hojo et al, 2010). MRJP2 and 7 were only detected in brains of nurses but not in foragers and they have transcripts in the worker mushroom bodies (Hojo et al, 2010). The expression of mrjp1 in the mushroom bodies was higher in worker bees sampled from colonies compared to isolated ones (Hojo et al, 2010), that are known to have a decreased learning ability (Ichikawa & Sasaki, 2003).…”

“…In spite of these multiple functions there is no specific functional conservation of the various yellow genes (Ferguson et al, 2011). Hojo et al (2010) suggested that MRJPs may have regulatory functions that control development and behaviour in addition to their nutritional role in RJ (Albert et al, 1999a). In addition to the MRJPs, the A. mellifera genome comprises 10 yellow genes that also have diverse expression patterns.…”

Comparative analyses of the major royal jelly protein gene cluster in three Apis species with long amplicon sequencing

“…In contrast, worker- and tissue-biased expression of mrjp1 – 7 indicates spatial and functional separation from mrjp8 and 9 , suggesting neofunctionalization of an ancestral duplicate. All worker- mrjps are predominantly expressed in heads, although their spatial expression patterns indicate further differentiation–with preferential expression in hypopharyngeal glands (for those genes encoding proteins with nutritional value) and/or the brain 39 . Moreover, elevated transcript abundances of some mrjps in brood-raising nurse bees compared with foragers (and vice versa ) indicate more specialized functions related to division of labor 13 , 32 .…”