Analysis of Transgenic Tobacco with Overexpression of Arabidopsis WUSCHEL Gene

The Arabidopsis WUSCIHIEL (WUS） gene plays a key role in the specification of the stem cellsin the shoot apical meristem (SAM). A cDNA of WUShas been amplified with the RT-PCR approach fromArabidopsis. The plant overexpression vector was constructed. It was driven by a dual enhanced CaMV35Spromoter. The construct was transformed into tobacco (Nicotiana tabacum L.) via Agrobacterium mediation.Dramatic phenotypic changes appeared in the WUS overexpression transgenic plants. Aberrant celldivisions and ectopic organogenesis could be found in almost every aerial parts of the transgenic tobaccoexcept the meristems and the inner two floral whorls. The data showed a highly conserved function of WUSin tobacco, and suggested that WUS is involved in organogenesis. The leaves were malformed, whichstrongly matched those only described previously for plants grown in the presence of polar auxin transportinhibitors. It suggested a possible function of WUS in leaf development. These results provide usefulinformation for functional analysis of WUS and important biotechnological implication as well.

Alternation in Lipid Composition of Wheat Leaves Induced by Phosphate Deficiency Is Related to Both Lipid Biosynthesis and Phosphatidylglycerol Degradation

In this study, the causes of the changes in lipid composition induced by different phosphatenutrient levels were investigated. Wheat plants were grown in phosphate-deficient and phosphate-suffcient conditions, respectively, and lipid compositions in the leaves of 9-day-old and 16-day-old plants wereanalyzed. We found that phosphate deficiency induced a dramatic change at the lipid levels in photosyntheticmembranes of wheat leaves and the extent of changes in lipid composition depended on the leaf ages.Phosphate deficiency induced a gradual decrease in PG and MGDG and a concomitant increase in DGDGand SQDG from the first leaf to the second and the third leaf on 16-day-old plants. In addition, as comparedto leaves grown under phosphate sufficient solution, PG content in the first leaf of 16-day-old plants wassignificantly lower than that of 9-day-old leaf with 2.5 mol% versus 5.5 mol% when these plants were grownunder phosphate deficient condition. From these results, it is suggested that the alternation in lipidcomposition in wheat leaves induced by phosphate deficiency is related to both lipid biosynthesis and PGdegradation. PG decrease in younger leaves is mainly due to insufficient phosphate supply for PG biosynthesis,while PG degradation mainly resulted in the PG decrease in older leaves.

Plasmodesmatal Dynamics in Both Woody Poplar and Herbaceous Winter Wheat Under Controlled Short Day and in Field Winter Period

Electron microscopic observation revealed that poplar (Populus deltoides Marsh.) and winterwheat ( Triticum aestivum L. cv. Seward 80004) plasmodesmatal structures significantly changed undershort day (SD, 8 h light) and in winter period, and such changes differed also noticeably between these twowoody and herbaceous plants. Under long day (LD, 16 h light), many plasmodesmata with strong stainappeared in the cell wall of both poplar apical buds and winter wheat young leaf tissues, and connections ofcytoplasmic endoplasmic reticulum (ER) with the ER in some plasmodesmata were observed. In addition,the typical “neck type” plasmodesmata were observed in winter wheat young leaf tissues, and their centraldesmotubules (appressed-ER) could be clearly identified. Under SD, many poplar plasmodesmata showedonly a partial structure in the cell wall and appeared to be discontinued; some plasmodesmata swelled in themid-wall, forming the cavity, and no appressed-ER appeared, in winter wheat, however, no noticeablealterations of plasmodesmata occurred, and the plasmodesmatal structure essentially remained the sameas it was under LD. In winter period, poplar plasmodesmata had a similar morphology as those observedunder SD, however, winter wheat manifested at least two types of significant plasmodesmatal alterations:one plugged by electron-dense materials and the other of reduced neck region compared to those underLD. The above dynamic difference of the two species plasmodesmata under SD and winter period revealedthe difference of their dormancy development under those environmental conditions.