Expression of FaXTH1 and FaXTH2 genes in strawberry fruit. Cloning of promoter regions and effect of plant growth regulators.

NARDI, C.*; VILLARREAL, N.* (CO-PRIMERA AUTORA); OPAZO, C.; MARTÍNEZ, G.; MOYA-LEÓN, A.; CIVELLO, P.

SCIENTIA HORTICULTURAE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 165 p. 111 - 122

0304-4238

Xyloglucan  endotransglycosylase/hydrolase  (XTH)  enzymes  are  involved  in the remodeling of plant cell wall hemicelluloses. With the aim to study the involvement of XTHs in strawberry  fruit ripening,  two  cDNAs (FaXTH1 and FaXTH2)  coding  putative XTH proteins  were  cloned and  the  expression  level of  both  genes was  analyzed on  different  plant  tissues  and during  ripening  of three  cultivars  that differ  in fruit  firmness:  Camarosa and Selva  (both firm  cultivars)  and  Toyonoka  (soft  cultivar). Bioinformatics and phylogenetic  analysis suggest  that  FaXTH1 would  have  xyloglucan  endo-transglycosylase  (XET)  as exclusive  activity,  while  FaXTH2 could be  either  a  strict  XET  enzyme  or  have  both  XET/XEH (xyloglucan  endo- hydrolase) activities. The expression profile of FaXTH1was similar during ripening of the three  cultivars analyzed; and a low transcript amount was detected in early ripening stages (LG and W) coinciding with  a  high  diminution  of  fruit  firmness. Nevertheless,  the  expression  level  of FaXTH1 was  significantly  higher  during  ripening  in  all  stages  in  Camarosa  and  in  LG,  W  and 100%  R  in  Selva,  in  comparison  to the  softer  cultivar  (Toyonoka). On  the  other  hand, not significant  differences  on FaXTH2  expression  levels  were  detected during  strawberry  fruit  ripening  and between  cultivars. These  results  suggest  that FaXTH1 and FaXTH2 might play different  roles  on  hemicellulose  metabolism  and  fruit  softening  in  strawberry.  In  addition, promoter regions of both genes were cloned and the effect of plant growth regulators on FaXTH1 and FaXTH2  gene  expression  was  evaluated. FaXTH1  and FaXTH2  gene  expression was significantly  up-regulated  when  fruit  were  treated  with  gibberelic  acid and abscisic  acid, and when the endogenous source of auxins was removed. On the other hand, the expression of both genes  decreased significantly in  fruit  treated  with  ethylene  while  the  opposite  situation was observed  in  fruit  treated  with 1-methylcyclopropene  (1-MCP),  an  inhibitor  of  ethylene perception.