Preliminary Studies On The Path Of Lignin Biosynthesis In Physcomitrella Patens Under Biotic Stress

Lignin is the most important biopolymer in vascular plants,which imparts rigidity, mechanical strength and resistance ofplants to abiotic and biotic stress. It is considered an importantevolutionary adaptation of plants during their transition from theaquatic environment to land. Bryophyte is the early land plant, someof which have a whole set of lignin biosynthesis gene, so bryophytecould biosynthesis lignin in some special condition. However, verylittle is known about whether lignin could be biosynthesized andthe biosynthesis mechanism in bryophyte. The purpose of this studywas to figure out the structure and the biosynthesis mechanism oflignin in bryophyte. The results from the present work provideduseful information in revealing the function and evolutionarymechanism of land plants, and laid the foundation for studyingresistance response of the early land plants.To understand the potential function of lignin biosynthesisgene in P. patens, during the defense responses against B. cinerea,the expressions of the genes which are critical to ligninbiosynthesis were analyzed by real-time fluorescent quantitativePCR technique. The results showed that, the expression levels ofC4H1, C4H2, CCR2, CCR3, CCR4, CCR5, CAD1, CAD3, CAD4, COMT2, COMT3, CCoAOMT1and CCoAOMT2were higher in test group than that in controlgroup, and the CCR1was expressed only in text group. These resultsindicated that the infection of B. cinerea. could induce P. patensto biosynthesize lignin.Moreover, lignin content was measured by UV spectrophotometry,and the structures of P. patens lignin were determined with DFRC(Derivatization Followed by Reductive Cleavage), gaschromatography-mass spectrometry (GC-MS). The results showed thatthe content of test group is higher than that of control group whichwere not infected by B. cinerea. But the standard structure (H,Gand S) of vascular plant have not been observed in P. patens afterbeing induced. This kind of defense response was also observed innonvascular plants. So the physio-biochemical changes as mechanismof resistance may exist in the early land plants.