[Responses of radial growth of Fraxinus mandshurica from different provenances to climate at Maoershan in Northeast China]. / 东北地区帽儿山种源实验林区不同种源水曲柳径向生长对气候的响应.

To understand the responses of radial growth of Fraxinus mandshurica from different provenances to climatic factors, we used the dendrochronological method to establish the standard chronologies of F. mandshurica from 20 provenances in Maoershan provenance test forest, and analyzed the differences in radial growth and their correlation with climate factors. The results showed that the overall trend of F. mandshurica chronologies from 20 provenances was generally similar. There were differences in growth amplitude, with the average radial growth of F. mandshurica from Dailing, Lushuihe and Sanchazi being the highest. The radial growth of F. mandshurica from 20 provenances was significantly positively correlated with the highest temperature in July and the average temperature in July except for Huinan. The radial growth of F. mandshurica from 14 provenances was significantly positively correlated with the precipitation in August. The radial growth of F. mandshurica was constrained by temperature and precipitation during the growing season. There was difference in radial growth among F. mandshurica from different provenances under drought stress. F. mandshurica from Wangqing, Dailing, and Hailin had stronger resistance to drought, while that from Wandianzi, Zhanhe, and Xinglong had better recovery ability after drought.

Progress on molecular mechanism of T-DNA transport and integration.

Agrobacterium-mediated transformation is probably the most widely used method to introduce genes into plants. Great progress has been made in recent years in studies on the mechanism of Agrobacterium-mediated transformation. Agrobacterium genetically transforms plants by transferring a portion of the resident Ti-plasmid, the T-DNA, to the plant. VirD2 and VirE2 accompany the T-DNA into the plant cell. Both proteins may aid in T-DNA transfer, nuclear targeting and integration into the plant genome. In recent years, some Arabidopsis rat (resistant to transformation) mutants are deficient in T-DNA integration according to some studies. These results showed that plant genes participate in the T-DNA transport and integration process. This paper discusses our current knowledge about the functions of virulence protein, namely VirD2 and VirE2, and plant genes in several aspect of Agrobacterium transformation. The paper discusses two different classes of integration patterns in detail: one is T-DNA right border being linked to genomic sequences by the VirD2 protein, the other is T-DNA integration via SDSA (synthesis-dependent strand-annealing). According to the latest studies we elaborated the T-DNA integration model based on genomic DSB (double-strand breaks) and proposed a new opinion about the mechanism of T-DNA integration.