pOsHAK1：OsFLN2 Expression Enhances the Drought Tolerance by Altering Sugar Metabolism in Rice

doi:10.13560/j.cnki.biotech.bull.1985.2021-1499

Abstract

Abstract:

Sugar synthesis and transport are key processes in plants response to drought stress. Ectopic expression of OsFLN2 gene driven by the promoter of OsHAK1 encoding a drought-enhanced potassium transporter may improve the growth of root system by affecting sugar metabolism in rice under drought stress. The net photosynthetic rate and sucrose phosphate synthase activity in the leaves of the pOsHAK1：OsFLN2 transgenic seedlings increased,but the sucrose contents of the leaves and roots markedly decreased and increased,respectively,resulting from the enhanced sucrose translocation in phloem under drought conditions. pOsHAK1：OsFLN2 transgenic lines demonstrated better tolerance to drought stress than wild-type（WT）ones. In comparison to WT,the transgenic lines had higher accumulations of proline,and lower level of lipid peroxidation. Further investigation revealed that in response to the drought treatment,stress-responsive genes were notably up-regulated in the transgenic plants,however,senescence-associated genes were less abundantly transcribed than in WT. The results suggest that improving sugar metabolism via the expression of pOsHAK1：OsFLN2 may be beneficial to increasing drought tolerance and rice productivity under drought stress.

Key words: rice, drought tolerance, sugar metabolism, inducible promoter

CHEN Guang, LI Jia, DU Rui-ying, WANG Xu. pOsHAK1：OsFLN2 Expression Enhances the Drought Tolerance by Altering Sugar Metabolism in Rice[J]. Biotechnology Bulletin, 2022, 38(8): 92-100.

Figures/Tables 9

Table 1 Primers used for RT-qPCR assays

基因名称Gene name	正向引物Forward primer（5'-3'）	反向引物Reverse primer（5'-3'）
UBQ5	CTCGCCGACTACAACATCCA	TCTTGGGCTTGGTGTACGTCTT
OsFLN2	CCGAATGGCTTCTCTTCTTCTC	GGCTCCTGATTGAGTTGGTACTACA
SGR	GCAATGTCGCCAAATGACG	GCTCACCACACTCATTCCCTAAAG
OsATG8a	AGCCCAGAAAAGGCCATCTT	CATCCTTGTTCTCTTCGTAGATTGC
OsSNAC1	GTCAAGACTGATTGGATCATGC	CCAATCATCCAACCTGAGAGA
OsMYB2	GAGCAGCGAGGAGGAGGT	TGTAGTTGACGAGCAGGAGGT

Fig. 1 Effects of drought stress on sugar metabolism in rice Rice seedlings were growing in normal IRRI solution for 6 weeks,then treated with 15% PEG for 10 d. A：Net photosynthetic rate（Pn）. B：Sucrose phosphate synthase（SPS）activity. C：Rate of sucrose export（SER）from the leaf. D-E：Sucrose contents of the leaf（D）and root（E）. The values are means ± SE of 5 replicates. Significant differences between normal and 15% PEG treatment are indicated with asterisks（P < 0.05）. FW：Fresh weight

Fig. 2 Construction of expression vector and process of genetic transformation in rice A：Construction map of expression vector. B-G：Callus induction（B,C）,sele-ction of transformed calli（D）,shoot regeneration from resistant calli（E,F）,and hardening of transgenic plants（G）,bar in B-D=2 cm,bar in E-G=3 cm. H：Iden-tification of positive transgenic lines by GUS staining in T0 generation,bar=1 cm

Fig. 3 Differential analysis of FLN2 expression and net photosynthetic rate between T1 generation of pHAK1：FLN2 transgenic lines and WT in response to drought stress Rice seedlings were growing in normal IRRI solution for 2 weeks,then treated with 15% PEG for 7 d. A：RT-qPCR analysis of endogenous OsFLN2 in the shoots of seedlings. UBQ5 was chosen as the reference sequence. B：Net photosynthetic rate. Results for the five null segregants were combined together as a second control（null segregant）,while five transgenic lines were combined together as pHAK1：FLN2. The values are means±SE. Significant differences at P < 0.05 are indicated with different letters

Fig. 4 Seedling growth of pHAK1：FLN2 transgenic lines compared with WT in response to drought stress A：Growth performance of the seedlings under normal and 15% PEG treatment,bar = 5 cm. B-C：Shoot（B）and root（C）biomass（dry weight）. The values are means ± SE of 5 replicates. Significant differences between WT and transgenic lines are indicated with asterisks（P < 0.05）and ns indicates non-significant differences at that level of significance. The same below

Fig. 5 Differential analysis of sugar metabolism between pHAK1：FLN2 transgenic lines and WT in response to drought stress A：Sucrose phosphate synthase（SPS）activity. B：Rate of sucrose export（SER）from the leaf. C-D：Sucrose contents of the leaf（C）and root（D）.The values are means±SE of 5 replicates

Fig. 6 Differential analysis of root system architecture be-tween pHAK1：FLN2 transgenic lines and WT in response to drought stress A：Total root length. B：Root surface area. The values are means ± SE of 5 replicates

Fig. 7 Differential analysis of water-content ability and lipid peroxidation between pHAK1：FLN2 trans-genic lines and WT in response to drought stress A：Relative water content. B：Water loss rate. C：Relative electrolyte leakage. D：Proline content. The values are means±SE of 5 replicates

Fig. 8 Differential analysis of expressions of senescence-associated genes and stress-responsive genes between pHAK1：FLN2 transgenic lines and WT in response to drought stress The genes assayed are（A）SGR,（B）ATG8a,（C）SNAC1 and（D）MYB2. UBQ5 is chosen as the reference gene. The values are means±SE of 3 replicates

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