JIA-2019-11

2510 LI Li-shu et al. Journal of Integrative Agriculture 2019, 18(11): 2505–2513 and hypocotyl length of the three transgenic lines were significant better than those of WT A . thaliana (Fig. 4-A–C and E). Compared with WT A . thaliana , transgenic plants exhibited larger leaf areas (Fig. 4-D and F). Taken together, these findings indicated that MieIF1A-b enhanced the growth of transgenic A . thaliana plants compared to that of WT plants. 3.5. Overexpression of MieIF1A-b improves salt stress tolerance in transgenic A. thaliana To further understand the salt tolerance of MieIF1A-b in transgenic A . thaliana plants under the treatments of different NaCl concentrations (0, 50, 100, and 200 mmol L –1 ). The growth of transgenic A . thaliana and WT plants showed no significant differences, and the survival rates of the seedlings of both plants were 100% under 0 mmol L –1 NaCl stress. Under 50 mmol L –1 NaCl stress, the growth of WT plants was affected, whereas transgenic plants grew well, and the survival rates of the four treated seedling materials remained 100%. Under 100 mmol L –1 NaCl stress, the seedling growth of WT plants was inhibited, and the survival rate of transgenic plants was higher than that of WT plants. The seedling survival rate of transgenic plants were 46.7–63.3%, whereas WT plants all died under the 200 mmol L –1 NaCl treatment. These findings indicate that transgenic A . thaliana could significantly improve salt tolerance during the seedling period (Fig. 5-A and B). 4. Discussion eIFs belong to a large gene family with many functions and are widespread in eukaryotes, including animals and plants (Wei et al. 1995; Davis and Schultz 1998; Dutt et al. 2015). eIF1A reportedly functions as a mRNAscanner, AUG initiation codon locator, and stress response regulator (Yang et al. 2017). Several eIF1A genes have been reported in plants, such as sugar beet (Rausell et al. 2003), A .  thaliana (Rausell et al. 2003), Porteresia coarctata (Latha et al. 2004), Rice (Huang et al. 2004; Diédhiou et al. 2008; Rangan et al. 2009), Festuca rubra (Diédhiou et al. 2008), L. chinensis (Sun and Hong 2013; Sun et al. 2015), and Tamarix hispida (Yang et al. 2017). The eIF1 gene encodes small proteins ranging from 12 to 17 kDa in different plants and is highly conserved among all eukaryotes (Sun et al. 2015). In our previous studies, we obtained two MieIF1A genes from SCoT differential display under abiotic stress (unpublished data). In this study, we isolated an eIF1A gene frommango. MieIF1A-b protein contained 144 amino acids with a molecular mass of 16.39 kDa (Fig. 1-A). Multiple sequence alignment showed that MieIF1A-b shares high homology with the eIF1 family found in a wide range of plants. Phylogenetic tree analysis showed that MieIF1A-b was more closely related to EgeIF1A . In rice, OseIF1A-1 and OseIF1A-2 are expressed in both vegetative and reproductive tissues, but the highest transcription level was found in flowering spikes (Huang et al. 2004). In Leymus chinensis , LceIF1 is expressed in all vegetative organisms, and the highest transcription level was found in roots (Sun and Hong 2013). In the present study, MieIF1A-b was expressed in all test tissues, and the transcription level of MieIF1A-b in flowers was much higher than that in vegetative organisms. This expression pattern was consistent with previous studies (Huang et al. 2004; Yang et al. 2017). We also found that the transcription level of MieIF1A-b continued to increase with mango fruit CK L4 L21 L10 A D C B E F Fig. 3 Detection of GUS staining in different tissues of Arabidopsis thaliana . A, leaf. B, stem, calyx. C, fruit pod. D, inflorescence. E, root. F, whole seedling plant. WT, wild-type A. thaliana . L4, L10, and L21 represent the three MieIF1A-b T 3 transgenic A. thaliana generations, respectively.