AUTHOR=Irfan Mohammad , Ghosh Sumit , Meli Vijaykumar S. , Kumar Anil , Kumar Vinay , Chakraborty Niranjan , Chakraborty Subhra , Datta Asis 

TITLE=Fruit Ripening Regulation of α-Mannosidase Expression by the MADS Box Transcription Factor RIPENING INHIBITOR and Ethylene

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00010

DOI=10.3389/fpls.2016.00010

ISSN=1664-462X

ABSTRACT=<p>α-Mannosidase (α-Man), a fruit ripening-specific <italic>N</italic>-glycan processing enzyme, is involved in ripening-associated fruit softening process. However, the regulation of fruit-ripening specific expression of <italic>α-Man</italic> is not well understood. We have identified and functionally characterized the promoter of tomato (<italic>Solanum lycopersicum</italic>) <italic>α-Man</italic> to provide molecular insights into its transcriptional regulation during fruit ripening. Fruit ripening-specific activation of the <italic>α-Man</italic> promoter was revealed by analysing promoter driven expression of <italic>beta-glucuronidase</italic> (<italic>GUS</italic>) reporter in transgenic tomato. We found that RIPENING INHIBITOR (RIN), a MADS box family transcription factor acts as positive transcriptional regulator of <italic>α-Man</italic> during fruit ripening. RIN directly bound to the <italic>α-Man</italic> promoter sequence and promoter activation/α-Man expression was compromised in <italic>rin</italic> mutant fruit. Deletion analysis revealed that a promoter fragment (567 bp upstream of translational start site) that contained three CArG boxes (binding sites for RIN) was sufficient to drive <italic>GUS</italic> expression in fruits. In addition, <italic>α-Man</italic> expression was down-regulated in fruits of <italic>Nr</italic> mutant which is impaired in ethylene perception and promoter activation/<italic>α-Man</italic> expression was induced in wild type following treatment with a precursor of ethylene biosynthesis, 1-aminocyclopropane-1-carboxylic acid (ACC). Although, <italic>α-Man</italic> expression was induced in <italic>rin</italic> mutant after ACC treatment, the transcript level was less as compared to ACC-treated wild type. Taken together, these results suggest RIN-mediated direct transcriptional regulation of <italic>α-Man</italic> during fruit ripening and ethylene may acts in RIN-dependent and -independent ways to regulate <italic>α-Man</italic> expression.</p>