Sucrose synthase activity in the sus1/sus2/sus3/sus4 Arabidopsis mutant is sufficient to support normal cellulose and starch production

Trabajo presentado en la Annual Meeting of The Japanese Society of Plant Physiologists, celebrada en Kyoto del 16 al 18 de marzo de 2012.

The involvement of sucrose synthase (SUS) in the synthesis of UDPglucose and ADPglucose linked to Arabidopsis cellulose and starch biosynthesis, respectively, has been questioned by Baratt et al. (2009), who showed that (a) SUS activity in wild type (WT) leaves is too low to account for normal rate of starch accumulation in Arabidopsis, and (b) different organs of the sus1/sus2/sus3/sus4 SUS mutant impaired in SUS activity accumulate WT levels of ADPglucose, UDPglucose, cellulose and starch. However, these authors assayed SUS activity under unfavorable pH conditions for the reaction. By employing favorable pH conditions for assaying SUS activity, we show that SUS activity is sufficient to support normal rate of starch accumulation in WT leaves. We also demonstrate that sus1/sus2/sus3/sus4 leaves display WT SUS5 and SUS6 expression levels. Furthermore, we show that SUS activity in leaves and stems of the sus1/sus2/sus3/sus4 and sus5/sus6 plants is ca. 85% of that of Wt leaves, which can support normal cellulose and starch biosynthesis. Our data disprove Barratt et al. claims, and are consistent with the possible involvement of SUS in cellulose and starch biosynthesis in Arabidopsis.

Peer Reviewed