Role Of Transcription Factors PnMYB1 And PnMYB2 In The Adaptation Of Antarctic Moss To Extreme Environments

MYB transcription factors play an important role in plant response to environmental stress.The Antarctic environment limits plant growth,and moss is one of its main terrestrial plants.In this research,two MYB transcription factors,PnMYB1 and PnMYB2,were screened from the transcriptome of Pohlia nutans after low-temperature stress,and their roles in plant adaptation to abiotic stress were studied.The specific results are as follows:PnMYB1 and PnMYB2 encode 410 and 329 amino acids,respectively,and both are R2R3MYB transcription factors.Multiple sequence alignment analysis showed that PnMYB1 shared 22.6%identity with PnMYB1,and they have a 21.0%-40.0%resemblance to MYB from other species.Evolutionary analysis shows that PnMYB1 and PnMYB2 share a common evolutionary ancestor with MYB from other species,and both are closely relative to the Physcomitrella patens MYB.The biological functions of PnMYB1 and PnMYB1 were studied by heterologously expressed in the moss model plant P.patens and the angiosperm model plant Arabidopsis thaliana.The results showed that under normal conditions,PnMYB1 and PnMYB2 had no effect on the growth and development of P.patens and Arabidopsis.Under salt and drought stress,the diameter of the gametophyte heterologously expressing PnMYB1 or PnMYB2 was larger than that of the wild type,while in the presence of ABA,the diameter of the gametophyte was smaller than that of the wild type.Using exogenous sucrose to induce the accumulation of anthocyanins,compared to the wild-type,heterologous expression of PnMYBl or PnMYB2 plants resulted in lighter hypocotyls and leaf colors,and reduced total flavonoid and anthocyanin content by approximately 18.0%and 17.0%,respectively.Under stress conditions,PnMYB1 increased the main root length ofA rabidopsis under salt,drought,and oxidative stress,and upregulated the expression of some antioxidant enzyme genes related to ROS clearance;Reduced sensitivity to ABA,manifested by an increase in germination rate and root length,and upregulated the expression level of some genes in ABA signaling pathway.PnMYB2 increased the length of main roots and the number of lateral roots in plants under oxidative stress,and of plants to NaCl,D-Manitol,and ABA resulted in lower germination rates and root length than wild-type plants.Both PnMYB1 and PnMYB2 increased the fresh weight,main root length,lateral root number,and chlorophyll content of Arabidopsis under low-temperature conditions of 16℃,while reducing MDA content and relative conductivity.Under cold-stress(4℃),compared with the wild-type,heterologous expression of PnMYBl or PnMYB2 significantly reduced the content of total flavonoids.flavonoids.and anthocyanins,as well as the increase in MDA.When treated at 4℃ for 6 h.the transcriptome heterologously expressing PnMYB1 or PnMYB2 had 625(517 and 108 genes were up-regulated and down-regulated,respectively)and 164(132 and 32 genes were significantly up-regulated and down-regulated,individually)differential genes compared with the wild type.The former mainly affected the starch and sugar metabolism pathways.followed by phenylpropane biosynthesis pathways.The differential genes of the latter are mainly enriched in the protein processing pathway distributed in the endoplasmic reticulum and glutathione metabolism pathway.In summary.PnMYB1 and PnMYB2 both improve the salt and drought resistance of P.patens and reduced the accumulation of total flavonoids and anthocyanins in plants.In Arahidopsis thaliana,PnMYB1 increases plant tolerance to salt,drought,oxidative stress.and ABA.and its mechanism is related to an increase in antioxidant levels;PnMYB1 negatively regulates the salt and drought resistance and ABA tolerance of Arahidopsis.In addition,both PnMYB1 and PnMYB2 can enhance the resistance of Arabidopsis to low-temperature.However.PnMYB1 may mainly upregulate the expression of genes related to cellular metabolic pathways.while PnMYB1 may enhance the plant’s tolerance to low temperature stress by increasing antioxidant capacity and promoting glutathione metabolism.In this study,we explored the biological functions of two MYB transcription factors from the Pohlia nutans in P.patens and Arabidopsis.It provides a theoretical basis for elucidating the role of MYB transcription factors in the adaptation of Antarctic moss to extreme environments,and has potential significance for exploring the application of excellent stress resistance genes in Antarctic moss.