Rice aquaporin OsPIP2;2 is a water‐transporting facilitator in relevance to drought‐tolerant responses

Abstract

In rice ( Oryza sativa ), the PLASMA MEMBRANE INTRINSIC PROTEIN (PIP) family of aquaporin has 11 members, OsPIP1;1 to OsPIP1;3, and OsPIP2;1 to OsPIP2;8, which are hypothesized to facilitate the transport of H 2 O and other small compounds across cell membranes. To date, however, only OsPIP1;2, OsPIP2;1, and OsPIP2;4 have been demonstrated for substrate selectivity in their source plant (rice). In this study, OsPIP2;2 was characterized as the most efficient facilitator of H 2 O transport across cell membranes in comparison with the other 10 OsPIPs. In concomitant tests of all OsPIP s, four genes ( OsPIP1;3 , OsPIP2;1 , OsPIP2;2 , and OsPIP2;4 ) were induced to express in leaves of rice plants following a physiological drought stress, while OsPIP2;2 was expressed to the highest level. After de novo expression in frog oocytes and yeast cells, the four OsPIP proteins were localized to the plasma membranes in trimer and tetramer and displayed the activity to increase the membrane permeability to H 2 O. In comparison, OsPIP2;2 was most supportive to H 2 O import to oocytes and yeast cells. After de novo expression in tobacco protoplasts, OsPIP2;2 exceeded OsPIP1;3, OsPIP2;1, and OsPIP2;4 to support H 2 O transport across the plasma membranes. OsPIP2;2‐mediated H 2 O transport was accompanied by drought‐tolerant responses, including increases in concentrations of proline and polyamines, both of which are physiological markers of drought tolerance. In rice protoplasts, H 2 O transport and drought‐tolerant responses, which included expression of marker genes of drought tolerance pathway, were considerably enhanced by OsPIP2;2 overexpression but strongly inhibited by the gene silencing. Furthermore, OsPIP2;2 played a role in maintenance of the cell membrane integrity and effectively protected rice cells from electrolyte leakage caused by the physiological drought stress. These results suggest that OsPIP2;2 is a predominant facilitator of H 2 O transport in relevance to drought tolerance in the plant.

Genome-Wide Identification of Aquaporin Genes in Adzuki Bean (Vigna angularis) and Expression Analysis under Drought Stress

“…In the roots of date palms, the expression of PdPIP1-1, PdPIP1-3, and PdPIP2-2 was induced during early drought [49]. Similar results were obtained for rice, where OsPIP2-2 showed higher expression under drought stress and CrPIP2-3 from bay bean (Canavalia rosea) also fit the expression pattern in transgenic plants [50,51]. Another research study found that SIPIP2-5, SIPIP2-7, and SIPIP2-1 were highly expressed in the roots [52].…”

Regulation of drought tolerance in Arabidopsis involves the PLATZ4‐mediated transcriptional repression of plasma membrane aquaporin PIP2;8

“…The AQPs primarily participate in maintaining cellular water homeostasis (Wang et al., 2020; Zargar et al., 2017). OsPIP2;2 is a predominant facilitator of water transport with relevance to drought tolerance (Bai et al., 2021). Transgenic tomato plants ectopically expressing MdPIP1;3 exhibit more engorged guard cells and closed stomata than WT plants, thereby enhancing their drought tolerance (Wang et al., 2017).…”

“…Interestingly, the expression of ZmPIP1;1 , ZmPIP1;5 and ZmPIP2;4 from Zea mays (maize) was transiently induced in the outer root tissue when maize plants regained osmotic potential following a mild salt treatment, thus suggesting that they might play a role in cellular water transport (Zhu et al., 2005). OsPIP2;2 from Oryza sativa (rice) mediates H 2 O transport in response to drought stress (Bai et al., 2021). Furthermore, the endoplasmic reticulum (ER) membrane‐anchored E3 ligase Rma1H1 was found to mediate the degradation of PIP2;1, leading to less trafficking of PIP2;1 from the ER to the PM and increasing drought tolerance in Arabidopsis (Lee et al., 2009).…”

Ubiquitin ligase OsRINGzf1 regulates drought resistance by controlling the turnover of OsPIP2;1

“…OsPIP1;3, responds strongly to drought stress and can be recruited to the plasma membrane by OsPIP2;2, to be a water‐transporting facilitator (Lian et al., 2004; Liu et al., 2020). Recent research has revealed the highest water transporting activity of OsPIP2;2 among the 11 PIPs in rice, which is beneficial to enhance the drought tolerance in rice protoplasts and seedlings (Bai et al., 2021). SIPs had a moderate water transport activity (Maurel et al., 2015).…”

“…In rice, there are total 33 AQPs (Sakurai et al., 2005). Some of them had been found to respond to drought (Bai et al., 2021; Lian et al., 2004), while the underlying regulation mechanism is unclear. Since AQPs are closely related to plant water status, regulation of rice AQPs might play a role in drought resistance.…”