The Study On Function Of GhMYB44 In Response To Drought Stress In Gossypium Hirsutum

Cotton has a long history of cultivation in China.It is not only the source of clothing for people,but also an essential oil and protein crop next to soybeans.Cotton is an important material related to the economy of China and people’s livelihood and occupies a very important position in the national economy.China has three major cotton producing regions(Xinjiang Cotton Region,Yellow River Basin Cotton Region,and Yangtze River Basin Cotton Region),with the main cotton producing region being Xinjiang Cotton Region.Cotton in Xinjiang is prone to drought stress due to abundant sunshine,arid climate and scarce rainfall,which affects its yield and fiber quality.Therefore,it is urgent to explore the key genes of cotton drought resistance,investigate the regulatory network of drought stress in cotton,and lay the foundation for cultivating drought resistant cotton varieties suitable for cultivation in Xinjiang cotton region.This study analyzed the drought stress transcriptome data of Gossypium hirsutum and identified the drought stress induced the expression of gene GhMYB44.GhMYB44 silenced plants were obtained by virus-induced gene silencing(VIGS),and heterologous overexpressed GhMYB44 in Arabidopsis.Therefore,we further analyzed the function and mechanism of GhMYB44 in cotton response to drought stress.The main findings were as follows:1.The expression level of GhMYB44 in different organs of cotton was analyzed by real-time fluorescence quantitative PCR(q RT-PCR).GhMYB44 was expressed in roots,stems,leaves,flowers(included petalstigmas,bracts,and stamens),and was predominantly expressed in leaves of vegetative organs and flowers of reproductive organs.After simulating drought treatment of cotton using PEG6000,we found that expression of GhMYB44 was induced in different Gossypium hirsutum varieties(S02,S08 and C312)after treatment with PEG6000,indicating that GhMYB44 might be involved in drought stress response.2.Silencing GhMYB44 by VIGS showed that the water loss rate and stomatal aperture of the silenced plants(TRV-GhMYB44)were significantly higher than those control plants(TRV-156).After PEG6000 treatment,the content of malondialdehyde in the leaves of the GhMYB44 silenced plants was significantly higher than that control plants,and the activity of antioxidant enzymes was significantly lower.Therefore,GhMYB44 can reduce water loss rate by regulating stomatal opening and alleviate oxidative damage caused by drought stress by regulating antioxidant enzyme activity,thereby positively participating in the cotton drought stress response process.3.The transgenic GhMYB44 Arabidopsis was obtained by dipping flower method,and its tolerance to drought stress was analyzed at germination and seedling stages.The results showed that GhMYB44 overexpression lines were more tolerant to mannitol simulated osmotic stress at germination stage than control lines.During the seedling stage,different lines were subjected to natural drought treatment,we found that the GhMYB44 overexpression lines was significantly more resistant to drought stress than control lines,and GhMYB44 overexpression lines had smaller stomatal length and width.4.In order to investigate whether GhMYB44 participates in drought stress through the ABA signaling pathway,the expression patterns of GhMYB44 in cotton after ABA treatment were analyzed.The results showed that GhMYB44 was induced to be expressed in different upland cotton varieties(S02,S08 and C312)under ABA treatment.The ABA sensitivity experiment showed that the germination rate of GhMYB44 overexpression lines to ABA was significantly higher than that of the control lines.After drought stress treatment in both GhMYB44 overexpression and WT lines,the expression levels of the negative regulatory factors At ABI1,At ABI2,and At PP2 CA in GhMYB44 overexpression lines were significantly lower than those in wild-type lines,indicating that GhMYB44 responds to drought stress through the ABA signaling pathway.In the study,through transgenic and gene interference techniques,we gradually revealed that GhMYB44 is involved as a negative regulator in drought and high salt response stress in plants.