Rice ERF OsEATB restricts GA biosynthesis - Plant Physiology
Rice ERF OsEATB restricts GA biosynthesis - Plant Physiology
Rice ERF OsEATB restricts GA biosynthesis - Plant Physiology
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and <strong>GA</strong>20ox2 at this growth stage. In elongating internodes of transgenic<br />
plants, OsCPS2 was down-regulated by 11.21-fold, while <strong>GA</strong>20ox2 was<br />
up-regulated by 2.03-fold, compared with their respective expression in the<br />
wild-type plants. In rice, the expression levels of XET (xyloglucan<br />
endotransglycosylase) and UROD (uroporhyrinogen decarboxylase) are<br />
up-regulated by <strong>GA</strong> treatment, while that of GOX (glycolate oxidase) is<br />
down-regulated (Yang et al., 2004). We investigated the effect of <strong>OsEATB</strong> on<br />
the expression of these three genes. Transgenic lines overexpressing<br />
<strong>OsEATB</strong> showed decreased expression of XET and UROD, but slightly<br />
increased expression of GOX, compared with their respective expression in<br />
the wild-type. These findings suggested that the <strong>GA</strong> response was suppressed<br />
in the transformants possibly due to the lack of bioactive <strong>GA</strong>s. SLENDER<br />
RICE1 [SLR1], the only DELLA protein in rice (Achard and Genschik, 2009),<br />
down-regulates the gibberellin signaling pathway (Fukao and Bailey-Serres,<br />
2008). We evaluated the effect of <strong>OsEATB</strong> overexpression on this gene, and<br />
found that expression of SLR1 was down-regulated in transgenic plants.<br />
Together, all of these results confirmed that <strong>OsEATB</strong> negatively regulates the<br />
internode elongation process, not via down-regulating <strong>GA</strong> sensitivity, but<br />
through restricting <strong>GA</strong> <strong>biosynthesis</strong>.<br />
Over-expression of <strong>OsEATB</strong> decreases the endogenous <strong>GA</strong> level in rice<br />
ent-Kaurene synthase A catalyzes the cyclization of GGDP to CDP, which is<br />
then converted to ent-kaurene before going through a series of processes to<br />
produce <strong>GA</strong> and various <strong>GA</strong> derivatives. Since <strong>OsEATB</strong> represses expression<br />
of OsCPS2, we determined the endogenous <strong>GA</strong> level in 3-leaf-stage 401006<br />
<strong>OsEATB</strong> transgenic plants and 9311 control plants, 6-leaf-stage 401006,<br />
401003 <strong>OsEATB</strong> transgenic plants and 9311 control plants. As shown in Table<br />
Ⅱ, the endogenous levels of all <strong>GA</strong>s tested (i.e. <strong>GA</strong>12, <strong>GA</strong>53, <strong>GA</strong>24, <strong>GA</strong>19, <strong>GA</strong>9,<br />
<strong>GA</strong>20, <strong>GA</strong>4, and <strong>GA</strong>1) were significantly lower in <strong>OsEATB</strong> transgenic plants<br />
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