An expression analysis profile for the entire sucrose synthase gene family in rice

Abstract

In rice three genes encoding for sucrose synthase (Sus) (EC 2.4.1.13) have previously been characterized, and a further three sequences for putative Sus genes reported. The current work confirms that these six genes comprise the entire rice Sus gene family. An expression analysis was conducted in various rice tissues using real-time quantitative RT-PCR. Sus transcripts were detected in a wide range of tissues and at different developmental stages, indicating that Sus is involved in numerous and diverse growth processes in the rice plant. SUS1 was predominantly expressed in elongating tissues including roots, developing leaves and internodes; a potential role for SUS1 in cellulose synthesis is discussed. SUS2 was shown to be expressed in a wide range of tissues, suggesting that it may perform a number of housekeeping role(s). In addition, overall Sus activity and expression of SUS2 increased significantly in seedlings germinated and grown in hypoxia (submerged conditions), suggesting a role in increasing sucrose metabolism as a response to environmental stress. SUS3 and SUS4 were predominantly expressed in the caryopsis, indicating potential roles in carbon allocation within the filling grain. Transcript levels of SUS5 and SUS6 were low in all tissues examined, and were suppressed in germinating shoots under submergence.