Rh-PIP2;1, a Rose Aquaporin Gene, Is Involved in Ethylene-Regulated Petal Expansion    

Abstract

Aquaporins are water channel proteins that facilitate the passage of water through biological membranes and play a crucial role in plant growth. We show that ethylene treatment significantly reduced petal size, inhibited expansion of petal abaxial subepidermal cells, and decreased petal water content in rose (Rosa hybrida 'Samantha'). Here, we report the isolation of a plasma membrane aquaporin (PIP) gene, Rh-PIP2;1, and characterized its potential role in ethylene-inhibited petal expansion. Rh-PIP2;1 is mainly localized on the plasma membrane and belongs to the class 2 subfamily of PIP proteins. We show that Rh-PIP2;1 is an active water channel. The transcripts of Rh-PIP2;1 are highly abundant in petal epidermal cells, especially in the abaxial subepidermal cells. The expression of Rh-PIP2;1 is highly correlated with petal expansion and tightly down-regulated by ethylene. Furthermore, we demonstrate that in Rh-PIP2;1-silenced flowers, petal expansion was greatly inhibited and anatomical features of the petals were similar to those of ethylene-treated flowers. We argue that Rh-PIP2;1 plays an important role in petal cell expansion and that ethylene inhibits petal expansion of roses at least partially by suppressing Rh-PIP2;1 expression.

Involvement of HbPIP2;1 and HbTIP1;1 Aquaporins in Ethylene Stimulation of Latex Yield through Regulation of Water Exchanges between Inner Liber and Latex Cells in Hevea brasiliensis

“…Some authors reported high expression of PIP2 in other tissues such as leaves (Sakurai et al, 2008), stigmas (Bots et al, 2005), and flower petals (Ma et al, 2008). To our knowledge, this is the first report of in situ hybridization of PIP2 in the stem liber of trees.…”

RhNAC2 and RhEXPA4 Are Involved in the Regulation of Dehydration Tolerance during the Expansion of Rose Petals

“…The silencing of RhNAC2 and RhEXPA4 in petals by VIGS was performed according to the procedures described by Ma et al (2008) with some modifications. For the construction of the RhNAC2 VIGS vector, we used a 351-bp fusion fragment combining 249 bp from the 59 end of the gene with 102 bp from its 39 end.…”

Identification and Characterization of Plasma Membrane Intrinsic Protein (PIP) Aquaporin Genes in Petals of Opening Carnation Flowers

“…In tulips, temperature-dependent flower opening and closing is associated with water uptake by petal tissues, which is suggested to involve AQP activity (Azad et al, 2004). Also direct evidence of the participation of a PIP (RhPIP2;1) in petal cell expansion was demonstrated in rose flowers (Ma et al, 2008). It is reasonable to anticipate the presence of genes for PIP that participate in water uptake during petal growth of opening carnation flowers.…”

“…Considering that DcPIP2;1 and DcPIP1;1 are expressed more abundantly than DcPIP1;3 as shown in Figure 2, the stable expression of DcPIP2;1 and DcPIP1;1 suggests that the expression level of these PIPs is high enough for flower opening. In rose petals, the role of PIP2 (Rh-PIP2;1) in the regulation of petal cell expansion was demonstrated (Ma et al, 2008). Since the expression of DcPIP2;1 is highest among DcPIP isoforms, it is plausible that DcPIP2;1 participates in petal growth in carnation flowers like Rh-PIP2;1 in rose petals.…”