Os02g0559800

Rice EL5 is an ATL family gene characterized by a transmembrane domain at the N-terminal and a RING-H2 finger domain (RFD), which exhibits ubiquitin ligase (E3) activity.

Annotated Information

Function

Rice EL5 is an ATL family gene characterized by a transmembrane domain at the N-terminal and a RING-H2 finger domain (RFD), which exhibits ubiquitin ligase (E3) activity. Overexpression of mutated EL5 gene arrests root growth in an E3-activity-dependent manner.Transgenic callus overexpressing mutated EL5 gene is morphologically auxin-irresponsive and similar to control callus treated with excess cytokinin.

'Figure 1. Overexpression of mutated EL5 encoding impaired E3 activity affects root formation.(a) Phenotypes of the regenerated shoots cultured on a hormone-free MS medium for 2 weeks [GUS as control and EL5(wt)] and 1 month (EL5C153A and EL5W165A). The inserted photograph shows a longer-cultured shoot base transformed with EL5W165A producing tillers. Bars = 1 cm.(b) Degrees of root formation of about 50 independent callus lines introduced with GUS (control), EL5(wt) and mutated EL5 genes. E3 activities deduced from in vitro ubiquitination assay (Katoh et al., 2005) are indicated.'

'Figure 4. Overexpression of mutated EL5 alters responses to auxin and cytokinin during regeneration. (a) Effects of auxin and cytokinin on the differentiation of callus cells. Calli transformed with only vector as control (left) and EL5W165A (right) were cultured on the regeneration medium with different a-naphthalene acetic acid and kinetin contents. The numbers of calli regenerating shoot with root (white bars), root only (gray bars), and shoot only (black bars) are presented as percentages of the total numbers of calli placed on the medium. The total numbers of calli counted are indicated in parenthesis. The average scores from two independent lines are plotted. The examination was repeated three times and typical results are shown.(b) Representative phenotypes of the regenerating calli described in (a).'

Expression

EL5 was mainly expressed in the basal region, and barely detected in the elongated shoot and root (Figure 3a). Signals of EL5 expression in rice seedlings were merely visible by in situ RNA hybridization, even though the Northern blot hybridization gave strong signals, as shown in Figure 3a. Thus, we analyzed the shoot base treated with JA and obtained signals in the cortex of the crown root primordia (Figure 3b), where cell death occurs in rice plants expressing mutated EL5.

'Figure 3.a'

'Figure 3. Tissue specificity and hormonal activation of EL5 expression.(a) Rice seedlings were treated with the indicated hormones, and total RNA from each sample was analyzed by Northern blotting. rRNAs from each sample stained with ethidium bromide are displayed at the bottom. Con,control plants treated with water or 10 mM MES buffer (pH 6.0); ABA, abscisic acid; BAP, 6-benzylaminopurine; GA3, gibberellin; JA, jasmonic acid; Et,ethephon; SA, salicylic acid; IAA, indole-3-acetic acid; BL, brassinolide.(b) In situ RNA hybridization of EL5. Cross sections were prepared from the shoot base of a 9-day-old rice plant treated with JA and hybridized with sense (left) or antisense (right) probe. Scale bars = 100 lm.'

Evolution

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Labs working on this gene

• Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai, 2-1-2, Tsukuba, Ibaraki 305-8602, Japan

References

Aloni, R., Aloni, E., Langhans, M. and Ullrich, C.I. (2006) Role of cytokinin and auxin in shaping root architecture: regulating vascular differentiation, lateral root initiation, root apical dominance and root gravitropism. Ann. Bot. (Lond) 97, 883–893.