In addition to autonomic dysfunction, some other mechanisms have also been suggested to be involved, such as reduced coronary flow caused by frequent postural BP drop, increased early subclinical atherosclerotic burden, abnormal nocturnal change in BP, and increased longstanding cardiovascular overload. These mechanisms are also needed to be confirmed by future studies. Our stratified analysis indicated that the significant association between OH and CHF incidence can be found in middle-age subjects and those with hypertension and DM at baseline. These results highlight the predictive effect of OH for future CHF in both the low-risk population and the high-risk population with known CHF risks. Although the results were not significant for elderly subjects and those without hypertension or DM, our study still found presence of OH increased the risk of future CHF in these subgroups. In our point of view, these insignificant results may be attributed to the small number of the included studies. Our study has some limitations which should be considered when interpreting the results. First, the number of studies included in the meta-analysis and stratifies analyses is small. The results for some subgroups should be interpreted with caution. Second, the CHF outcomes of the included studies were defined as CHF hospitalization or death. So, some less severe or asymptomatic CHF cases may not be included. Third, our meta-analysis is based on observational studies. Hence, we cannot exclude the chance, residual or unmeasured confounding. However, since there seemed to be no evidence-based effective intervention for the treatment of OH, it is difficult to confirm our results in a large randomized trial. Fourth, potential therapy to OH and many kinds of medications such as antihypertensive reinforces possibility satisfactory therapy await discovery fundamental proximal pathogenesis medication may affect the risk between OH and CHF. However, as indicated in a recent review, many commonly recommended interventions for OH have a limited evidence base supporting their use, and the effects have not been confirmed. Also, effects of some antihypertensive medications on OH, such as angiotensin-converting enzyme inhibitors, are not always consistent. Furthermore, potential treatment for OH was not specified in the included studies, although the use of antihypertensive medications was adjusted in two of the studies when estimating the association between OH and incident CHF. We acknowledged that lack of controlling for potential treatment to OH and other medications is an important limitation of our 
study. Fifth, we did not have data on individual studies to assess CHF etiology or types. Nevertheless, our study also has numerous strengths, including the relative high quality of studies included, a large pooled sample size, robustness of the results in sensitivity analysis, and use trimand-till analysis to handle potential publication bias. In conclusion, results of our meta-analysis confirmed that presence of OH is related to a significant increased risk for development of CHF in the future, especially for the middle-age subjects and those with morbidities such as hypertension and DM. Studies are needed to explore the potential mechanisms underlying this association. More importantly, screen for OH may be of great clinical significance for the early identification of subjects at higher risk for development of CHF. Introduction of new traits into plants via genetic transformation has become an important technology for plant improvement. Proper preservation of transgenes and extension of the new traits to the next generation after the plant growth season are important for the wide use of transgenic technology. Herbaceous plants, especially annual plants, grow once a year. At the end of the growth season, plants die and are disposed, and the transgenes can be lost. However, new genes in plants may be stored and preserved in seeds and then passed to the next generation.