Specific alien plant species predominantly deliver nectar sugar and pollen but are not preferentially visited by wild pollinating insects in suburban riparian ecosystems.

The invasion of alien plants has been rapidly proceeding worldwide due to urbanisation. This might be beneficial to wild pollinating insects, since some alien plant species have large flowers and/or long flowering periods, which can increase nectar sugar and pollen availability. To determine the relative contribution of alien plants to floral resource supply and whether resource-rich alien plants, if any, serve as an important food source of pollinating insects, we performed year-round field observations in suburban riverbanks. We quantified the per-unit-area availability of nectar sugar and pollen delivered by alien and native flowering species and counted wild flower visitors (bees and wasps, hoverflies and butterflies) per plant species. The available nectar sugar and pollen per area were predominantly delivered by a few specific alien species, and the relative contribution of other species to floral resource provision was low throughout the period that wild flower visitors were observed. Nonetheless, the resource-rich alien plants were not visited by as many insects as expected based on their contribution to resource provision. Rather, on a yearly basis, these plants received equal or even fewer visits than other flowering species, including resource-poor natives. We show that despite their great contribution to the gross floral resource supply, resource-rich alien plants do not serve as a principal food source for wild pollinating insects, and other plants, especially natives, are still needed to satisfy insect demand. For the conservation of pollinating insects in suburban ecosystems, maintaining floral resource diversity would be more beneficial than having an increase in gross floral resources by allowing the dominance of specific alien plants.

Ectopic expression of mutated type 2C protein phosphatase OsABI-LIKE2 decreases abscisic acid sensitivity in Arabidopsis and rice.

Abscisic acid (ABA) is a phytohormone that is necessary for stress adaptation. Recent studies have reported that attenuated levels of ABA improved grain yield and seedling growth under low temperature in cereals. To improve plant growth under low temperature, we attempted to generate ABA-insensitive transgenic rice by expressing a clade A type 2C protein phosphatase (OsPP2C), OsABIL2, with or without the mutation equivalent to the Arabidopsis abi1-1 mutation. A yeast two-hybrid assay revealed that the interaction between OsABIL2 and a putative rice ABA receptor, OsPYL1, was ABA-dependent, and the interaction was lost with amino acid substitution from glycine to aspartic acid at the 183rd amino acid of the OsABIL2 protein, corresponding to abi1-1 mutation. The constitutive expression of OsABIL2 or OsABIL2G183D in Arabidopsis or rice decreased ABA sensitivity to differing degrees. Moreover, the transgenic rice expressing OsABIL2G183D exhibited improved seedling growth under low temperature, although the transgenic lines showed unfavorable traits, such as viviparous germination and elongated internodes. These results indicated that the introduction of abi1-1 type dominant mutation was also effective in OsABIL2 at decreasing ABA sensitivity in plants, and the attenuation of ABA sensitivity could be an alternative parameter to improve rice performance under low temperatures.