Sugar starvation- and GA-inducible calcium-dependent protein kinase 1 feedback regulates GA biosynthesis and activates a 14-3-3 protein to confer drought tolerance in rice seedlings

Abstract

Germination followed by seedling growth constitutes two essential steps in the initiation of a new life cycle in plants, and in cereals, completion of these steps is regulated by sugar starvation and the hormone gibberellin. A calcium-dependent protein kinase 1 gene (OsCDPK1) was identified by differential screening of a cDNA library derived from sucrose-starved rice suspension cells. The expression of OsCDPK1 was found to be specifically activated by sucrose starvation among several stress conditions tested as well as activated transiently during post-germination seedling growth. In gain- and loss-of-function studies performed with transgenic rice overexpressing a constitutively active or RNA interference gene knockdown construct, respectively, OsCDPK1 was found to negatively regulate the expression of enzymes essential for GA biosynthesis. In contrast, OsCDPK1 activated the expression of a 14-3-3 protein, GF14c. Overexpression of either constitutively active OsCDPK1 or GF14c enhanced drought tolerance in transgenic rice seedlings. Hence, our studies demonstrated that OsCDPK1 transduces the post-germination Ca(2+) signal derived from sugar starvation and GA, refines the endogenous GA concentration and prevents drought stress injury, all essential functions to seedling development at the beginning of the life cycle in rice.

A rice calcium-dependent protein kinase OsCPK9 positively regulates drought stress tolerance and spikelet fertility

“…Our results suggested that OsCPK9 is a positive regulator of the responses to drought, osmotic, and dehydration stresses (Figure  2; Additional file 1: Figure S2 and S3). These results are consistent with those of previous studies on some other CDPK genes that positively regulate drought stress tolerance [18,24,28]. …”

“…SPK is involved in regulating the metabolic pathway responsible for the conversion of sucrose into storage starch in immature seeds [27]. OsCDPK1 negatively regulates the expressions of enzymes required for GA biosynthesis and seed size, but positively regulates drought stress tolerance through the14-3-3 protein [28]. However, it is unclear whether CDPKs play a role in regulating spikelet fertility.…”

Genome-wide survey and expression analysis of the calcium-dependent protein kinase gene family in cassava

“…Calcium-dependent seed-specific protein kinase (SPK) functions in the regulation of the metabolic pathway responsible for sucrose to storage starch conversion in immature seeds, thus making it as a crucial regulator of seed development in rice (Asano et al 2002). OsCDPK1 was found to be a negative factor of GA biosynthesis and seed size in rice (Ho et al 2013). Recently, OsCPK9 was reported to improve pollen viability, thereby increasing spikelet fertility in rice (Wei et al 2014).…”

Proteomic Analysis Reveals Differences in Tolerance to Acid Rain in Two Broad-Leaf Tree Species, Liquidambar formosana and Schima superba

“…Free Ca ion within cell is a second messenger for conveying internal and external signals by Ca sensors that subsequently regulate diverse cellular processes in plants [17]. Calmodulin (CaM) and calcium-dependent protein kinase (CDPK), two major types of Ca sensor, play important roles in Ca signaling and further response to diverse stresses in plants [51]. Saijo et al [52] found that over-expression of OsCDPK gene enhanced tolerance to cold, salt and drought in transgenic rice.…”