Disruption of a gene for rice sucrose transporter, OsSUT1, impairs pollen function but pollen maturation is unaffected

Abstract

Sucrose transporters (SUTs) are known to play critical roles in the uptake of sucrose from the apoplast in various steps of sugar translocation. Because developing pollen is symplastically isolated from anther tissues, it is hypothesized that SUTs are active in the uptake of apoplastic sucrose into pollen. To investigate this possibility, a comprehensive expression analysis was performed for members of the SUT gene family in the developing pollen of rice (Oryza sativa L.) using real-time RT-PCR combined with a laser microdissection technique. Among the five SUT genes, OsSUT1 and OsSUT3 were found to be preferentially expressed and had temporal expression patterns that were distinct from each other. Expression of OsSUT1 in pollen was confirmed by a promoter–GUS fusion assay. The physiological function of OsSUT1 in pollen was further investigated using retrotransposon insertion mutant lines. While the homozygote of disrupted OsSUT1 (SUT1–/–) could not be obtained, heterozygote plants (SUT1+/–) showed normal grain filling. Their progeny segregated into SUT1+/– and SUT1+/+ with the ratio of 1:1, suggesting that the pollen disrupted for OsSUT1 is dysfunctional. This hypothesis was reinforced in vivo by a backcross of SUT1+/– plants with wild-type plants and also by in vitro pollen germination on the artificial media. However, starch accumulation during pollen development was not affected by disruption of OsSUT1, suggesting that the sugar(s) required for starch biosynthesis is supplied by other sugar transporters.

Analysis of Sugar Content and Expression of Sucrose Transporter Genes (<i>OsSUTs</i>) in Rice Tissues in Response to a Chilling Temperature

“…has reportedly had effects on the pollen function (e.g., pollen germination) or on the growth and production of filled grain, resulting in decreased grain weight (Hirose et al 2010, Ishimaru et al 2001, Scofield et al 2002. These reports also suggest that the decrease in expression levels of OsSUT1 in rice sheaths at the booting stage observed in our study may affect the development of anthers, including pollens.…”

Down-Regulating CsHT1, a Cucumber Pollen-Specific Hexose Transporter, Inhibits Pollen Germination, Tube Growth, and Seed Development

“…To date, there have been a number of studies conducted on the roles of SUTs on pollen tube germination and growth (Ylstra et al, 1998;Schneidereit et al, 2003Schneidereit et al, , 2005Scholz-Starke et al, 2003;Sivitz et al, 2008;Hirose et al, 2010). Several SUTs have been detected in pollen or pollen tubes (Lemoine et al, 1999;Stadler et al, 1999;Hackel et al, 2006;Sivitz et al, 2008;Hirose et al, 2010).…”

Impaired Function of the Tonoplast-Localized Sucrose Transporter in Rice, OsSUT2, Limits the Transport of Vacuolar Reserve Sucrose and Affects Plant Growth

“…For instance, AtSUC1 (Stadler et al, 1999;Sivitz et al, 2008), NtSUT3 (Lemoine et al, 1999), and Plantago major SUC1 (PmSUC1; Lauterbach et al, 2007) are expressed in pollen tubes, suggesting their function in growing pollen tubes. From the SUT3 clade, OsSUT1 is expressed in pollen and in nucellar projections and aleurone tissues of immature seeds and thus likely functions in apoplastic Suc transport into these sink organs (Furbank et al, 2001;Hirose et al, 2010). HvSUT1 is also mainly expressed in maternal nucellar projections and in the filial transfer cells of barley (Weschke et al, 2000), suggesting that it has similar functions.…”

“…The rice genome contains five SUTs, OsSUT1 to OsSUT5 (Aoki et al, 2003). To date, however, only OsSUT1 has been characterized in detail (Scofield et al, 2007;Hirose et al, 2010;Sun et al, 2010). We aimed to increase our understanding of Suc storage and transport in rice, an important worldwide crop.…”