Differential gene expression between hybrids and their parents is considered to be associated with heterosis. However,the physiological functions and possible contribution to heterosis of these differentially expressed genes are unknown.We have isolated one hybrid upregulated gene encoding putative wheat ADP-ribosylation factor, designated TaARF. In thisstudy, real-time quantitative reverse transcription-polymerase chain reaction analysis indicated that the TaARF transcriptwas preferentially expressed in root, node and crown, and the accumulation of TaARF mRNA in hybrid was more than1.5-fold higher than that in two parents. In order to understand possible roles of the putative wheat ARF gene, TaARFwas overexpressed in Arabidopsis, and the transgenic plants were characterized. We show that ectopic overexpression ofTaARF in Arabidopsis leads to increased leaf area, increased growth rate and earlier transition to flowering, suggestingthat TaARF plays significant roles in growth and development. This study provides evidence demonstrating that TaARFplays important roles in gr owth and development and we speculate that the upregulated expression of this gene mightcontribute to the heterosis observed in wheat root and leaf growth.
Yingyin Yao Zhongfu Ni Jinkun Du Zongfu Han Yan Chen Qingbo Zhang Qixin Sun
Heterosis in internode elongation and plant height is commonly observed in hybrid plants, but the molecular basis for the increased internode elongation in hybrids is unknown. In this study, midparent heterosis in plant height was determined in a wheat diallel cross involving 16 hybrids and 8 parents, and real-time PCR was used to analyze alterations in gene expression between hybrids and parents. Significant heterosis of plant height and the first internode in length were observed for all 16 hybrids, but the magnitude of heterosis was variable for different cross combinations. Analysis revealed that the heterosis of the first internode was significantly correlated to that of plant height (r = 0.56, P < 0.05), suggesting that the increased elongation of the first internode is the major contributor to the heterosis in plant height. Real-time PCR analysis exhibited that significant difference in heterosis of gene ex- pression was observed among all cross combinations. Moreover, heterosis of the first internode in length was correlated significantly and positively with expression heterosis of KS, GA3ox2-1, GA20ox2, GA20ox1D, GA-MYB and GID1-1, but significantly and negatively with expression heterosis of GAI and GA2ox-1, which is consistent with our recently proposed model of GAs and heterosis in wheat plant height, suggesting the alteration of GA biosynthesis and response pathways might be responsible for the observed heterosis in plant height.
WANG XiuLi1,2, YAO YingYin1,2, PENG HuiRu1,2, ZHANG Yi1,2, LU LaHu1,2, NI ZhongFu1,2 & SUN QiXin1,2 1 State Key Laboratory for Agrobiotechnology, Key Laboratory of Crop Heterosis and Utilization (MOE), Key Laboratory of Crop Genomics and Genetic Improvement (MOA), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural Univer- sity, Beijing 100193, China
14-3-3 proteins belong to a family of phosphoserine/threonine-binding modules and participate in a wide array of signal transduction and regulatory events. Our previous study demonstrated that Ta14-3-3 was significantly down-regulated in leaf and root tissues of hybrid wheat at the tillering stage. In this paper, three homoeologous Ta14-3-3 genes were cloned from common wheat (Triticum aestivum L., 2n=6x=42, AABBDD) and mapped on chromosomes 2A, 2B, and 2D, respectively. Transgenic Arabidopsis plants ectopically overexpressing Ta14-3-3 displayed shorter primary roots, delayed flowering and retarded growth rates, indicating that Ta14-3-3 acted as a growth inhibitor in Arabidopsis. In wheat, Ta14-3-3 was down-regulated in roots and leaves of hybrids as compared to their parental lines. We proposed that Ta14-3-3 proteins might regulate growth vigor in hybrid wheat.
LI JingSONG Su-shengZHAO Yu-shengGUO Wei-weiGUO Guang-huiPENG Hui-ruNI Zhong-fuSUN Qi-xinYAO Ying-yin
