Abstract: 【Objective】 In previous work, we had proven that a bZIP type transcription factor gene, AtTGA4 can improve the drought resistance and low nitrogen tolerance of transgenic Arabidopsis. In this study, AtTGA4 was transformed into wheat to identify the tolerance of transgenic wheats to low phosphorus stress in field. At the same time, the physiological mechanism of AtTGA4 gene to improve the stress resistance of transgenic wheats was analyzed, which laid the foundation for the molecular breeding of wheat tolerant to low phosphorus stress. 【Method】Used particle bombardment method of minimal expression box to co-transform AtTGA4 and marker gene Bar into wheat variety Shi4056. After transformation, we screened many transgenic wheat lines without Bar gene and with AtTGA4 gene through PCR assay. In field experiment, base on fertilizer nutrient content in soil we applied different levels of phosphate, which led to low phosphorus stress in soil. AtTGA4 transgenic wheat lines were tested under low phosphorus. During the flowering stage some physiological indexes were identified such as light efficiency of the light system Ⅱ (Fv/Fm), the relative content of chlorophyll (SPAD) and crown the temperature difference (CTD), and other agronomic traits were investigated, during mature stage such as plants height, tiller number, grains per spike in mature period, and some values such as the grain yield and phosphorus concentration and phosphorus uptake in different components in wheat (root, stem, leaf and grain) were measured and data statistic analysis were completed. 【Result】 PCR analysis showed that AtTGA4 gene had been stable heritability for T₄ generation in Shi4056 and four stable transgenic lines were obtained. According to the results of soil nutrient content, 812.39 kg·hm^-2 of superphosphate was applied to normal plots, and no phosphorus was applied in low phosphorus treatment plots. The statistical results of yield and agronomic characters showed that the grain yield of AtTGA4 transgenic lines L1 and L2 increased compared to wild type (WT) significantly under normal condition and low phosphorus stress. Under normal conditions the yield of transgenic wheat increase of 5.3%-8.6%, and under low phosphorus stress grain yield of transgenic wheat increased of 4.4%-7.7%. Thousand seed weight of AtTGA4 transgenic wheat increased significantly than WT. The results of physiological indexes assay in field showed that the Fv/Fm and CTD of transgenic lines L1 and L2 were significantly better than those of WT under the condition of low phosphorus, while SPAD had no significant difference. We found that under low phosphorus stress WT were in early grain filling than the transgenic wheat, and the ears turn yellow early in WT than that in transgenic wheat plants. The phosphorus content assay during the late mature stage showed that the phosphorus concentration in the stems of L1 and L2 of transgenic lines increased significantly compared with that of WT under the condition of low phosphorus, but there was no significant difference in other tissues. Under the condition of low phosphorus, the total phosphorus content in stems and leaves and grains of two transgenic lines was higher than that of WT, and the total phosphorus content in the aerial part increased by 6.38%-17.47%. qRT-PCR results of AtTGA4 in transgenic wheat showed that the expression of AtTGA4 in Line 2 (L1) was 0.69 times lower than that of Line 1 (L1). 【Conclusion】 The above results showed that under the condition of low phosphorus stress, AtTGA4 can improve the uptake and transportation of phosphorus in transgenic wheat plants, and increase the yield of transgenic plants, and further enhance the tolerance of transgenic wheat to low phosphorus stress.

Key words: transgenic wheat, AtTGA4, low phosphorus stress, yield, physiological index