| Dioecious plants are advanced forms of plant evolution.In the wild environment,many male and female individuals will evolve different forms that adapt to the sex due to the different investment in reproduction,and the morphological differences related to resistance are one of them.This is also the external manifestation of the differential resistance of male and female individuals.However,the morphological and structural differences between male and female individuals of the artificially cultivated sibling lines are relatively small.Whether there are still differences in resistance between sib plants and the mechanism of differential resistance is still unclear.For this reason,we took the sib Populus×euramericana Nanlin-1388 and Nanlin-895 to explore their physiological differences in response to simulated drought conditions and the differences in the regulation of key genes related to drought.It is expected to reveal the mechanism of resistance differences in dioecious plants at the molecular level.Our results show that the physiological response of male cuttings was stronger than that of female after drought stress.Water deficiency significantly inhibited both height and diameter in female and male cuttings,and the inhibitory effect of female was greater than that of male.In addition,the leaves of male were intact,while the leaves of female were mostly curled and chlorosis after 90 days drought treatment.In terms of photosynthesis,the photosynthetic capacity of sib P.×euramericana was both inhibited by drought stress.But compared to the female,male maintained higher A and C_i,and under severe drought condition,the Fv/Fm,Ф,q P of male were significantly higher than that of female,NPQ was significantly lower than female.This result is consistent with the content of photosynthetic pigment,our results show that the contents of chlorophyll a,chlorophyll b and total chlorophyll of male were significantly higher than that of female.There are also differences between males and females in the elimination of ROS produced by drought stress.The activities of SOD and POD of male were significantly higher than that of female after drought stress,but the activities of CAT were significantly lower than that of female,which showed different mechanisms for scavenging ROS.Moreover,the content of proline,MDA,and the degree of cell membrane damage in male under drought condition are generally lower than female.To explore the molecular mechanism of the differences in physiological responses of sib P.×euramericana to drought,we selected 6 genes closely related to photosynthesis and antioxidant capacity for transcription level analysis.The results of q RT-PCR showed that the six genes of male and female cuttings had different degrees of regulation.The expression of CAT and GST of female were significantly higher than that of male under mild drought stress,but the differences disappeared and the expression of SOD was significantly lower than male under severe drought condition.It shows that the antioxidant system of female P.×euramericana is more sensitive to mild drought,and the sib cuttings may adopt different free radical scavenging strategies under drought conditions,but male P.×euramericana can maintain stronger antioxidants under severe drought condition.In addition,the expression of Psb X1 in male was significantly higher than that in female under severe drought stress,indicating that male can maintain stronger photosynthetic capacity through the regulation of Psb X1.At the same time,the expression of EDS1 in female was significantly higher than male under mild drought stress,but the difference disappeared under severe drought condition.It also shows that female plants are sensitive to water deficiency,which initiate the apoptosis program to deal with the drought stress under mild drought condition.Furthermore,the expression of b HLH35 of female was significantly induced by drought,and the difference between male and female reached extreme significant level.This reflects that female may have different molecular regulation methods for drought compare with male.In summary,the physiological differences between sib P.×euramericana are basically consistent with the differences in the transcriptional levels of drought-related genes.Female was sensitive to changes in soil water content,and male exhibited stronger resistance under drought stress.Moreover,the differential expression of drought-related genes also reflects that the male and female P.×euramericana may have chosen different molecular regulation methods in response to drought stress.The fundamental reason for these differences is inseparable from the sex determination mechanism of P.×euramericana. |
PDF Full Text Request