RESUMO
The improvement of cold adaptation has contributed to the increased growing area of rice. Standing variation and de novo mutation are distinct natural sources of beneficial alleles in plant adaptation. However, the genetic mechanisms and evolutionary patterns underlying these sources in a single population during crop domestication remain elusive. Here we cloned the CTB2 gene, encoding a UDP-glucose sterol glucosyltransferase, for cold tolerance in rice at the booting stage. A single standing variation (I408V) in the conserved UDPGT domain of CTB2 originated from Chinese Oryza rufipogon and contributed to the cold adaptation of Oryza sativa ssp. japonica. CTB2 is located in a 56.8 kb region, including the previously reported gene CTB4a in which de novo mutation arose c. 3200 yr BP in Yunnan province, China, conferring cold tolerance. Standing variation of CTB2 and de novo mutation of CTB4a underwent stepwise selection to facilitate cold adaptation to expand rice cultivation from high-altitude to high-latitude regions. These results provide an example of stepwise selection on two kinds of variation and describe a new molecular mechanism of cold adaptation in japonica rice.
Assuntos
Oryza , Alelos , China , Domesticação , Genes de Plantas , Oryza/genética , Seleção GenéticaRESUMO
Grain length is one of the determinants of yield in rice and auxin plays an important role in regulating it by mediating cell growth. Although several genes in the auxin pathway are involved in regulating grain length, the underlying molecular mechanisms remain unclear. In this study we identify a RING-finger and wd40-associated ubiquitin-like (RAWUL) domain-containing protein, Gnp4/LAX2, with a hitherto unknown role in regulation of grain length by its influence on cell expansion. Gnp4/LAX2 is broadly expressed in the plant and subcellular localization analysis shows that it encodes a nuclear protein. Overexpression of Gnp4/LAX2 can significantly increase grain length and thousand-kernel weight. Moreover, Gnp4/LAX2 physically interacts with OsIAA3 and consequently interferes with the OsIAA3-OsARF25 interaction in vitro and in vivo. OsIAA3 RNAi plants consistently exhibit longer grains, while the mutant osarf25 has small grains. In addition, OsARF25 binds to the promoter of OsERF142/SMOS1, a regulator of organ size, and positively regulates its expression. Taken together, the results reveal that Gnp4/LAX2 functions as a regulator of grain length through participation in the OsIAA3-OsARF25-OsERF142 pathway and that it has potential value for molecular breeding in rice.
Assuntos
Grão Comestível/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/genética , Proteínas de Plantas/genética , Transdução de Sinais/genética , Sequência de Aminoácidos , Grão Comestível/genética , Proteínas Nucleares/metabolismo , Oryza , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/química , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Alinhamento de SequênciaRESUMO
A horizontal, table-sized computer display was used to examine one- and two-finger search performances. 31 college students participated in a basic computer operation and target landmark search task. The mean completion times of the target landmark search task were analyzed by a repeated-measures analysis of variance with the following factors: input device, environmental familiarity, and cue. Compared to the mouse, directly touching the computer display with one finger was inefficient when the task required more precise human-computer interactions, such as selecting small objects, or complicated tasks such as searching for targets in a computerized geographic application. However, directly touching the computer display with two fingers, one finger of each hand, appears efficient in complicated tasks. Additionally, familiar and cued environments can aid in the target landmark search task especially when searching within the cued conditions. However, the unfavorable effect of using a one-finger touch technique in searching may eliminate such cue effects.