Natural variation in the promoter of rice calcineurin B‐like protein10 (OsCBL10) affects flooding tolerance during seed germination among rice subspecies

Abstract

Rice (Oryza sativa L.) has two ecotypes, upland and lowland rice, that have been observed to show different tolerance levels under flooding stress. In this study, two rice cultivars, upland (Up221, flooding-intolerant) and lowland (Low88, flooding-tolerant), were initially used to study their molecular mechanisms in response to flooding germination. We observed that variations in the OsCBL10 promoter sequences in these two cultivars might contribute to this divergence in flooding tolerance. Further analysis using another eight rice cultivars revealed that the OsCBL10 promoter could be classified as either a flooding-tolerant type (T-type) or a flooding-intolerant type (I-type). The OsCBL10 T-type promoter only existed in japonica lowland cultivars, whereas the OsCBL10 I-type promoter existed in japonica upland, indica upland and indica lowland cultivars. Flooding-tolerant rice cultivars containing the OsCBL10 T-type promoter have shown lower Ca flow and higher α-amylase activities in comparison to those in flooding-intolerant cultivars. Furthermore, the OsCBL10 overexpression lines were sensitive to both flooding and hypoxic treatments during rice germination with enhanced Ca flow in comparison to wild-type. Subsequent findings also indicate that OsCBL10 may affect OsCIPK15 protein abundance and its downstream pathways. In summary, our results suggest that the adaptation to flooding stress during rice germination is associated with two different OsCBL10 promoters, which in turn affect OsCBL10 expression in different cultivars and negatively affect OsCIPK15 protein accumulation and its downstream cascade.

The Molecular Regulatory Pathways and Metabolic Adaptation in the Seed Germination and Early Seedling Growth of Rice in Response to Low O2 Stress

“…OsCBL10, another member of the rice CBL family, has been reported to be involved in flooding stress response during rice germination by comparing flooding-tolerant (Low88) with flooding-intolerant (Up221) cultivars. The natural variation in the OsCBL10 promoter is associated with the tolerance of anaerobic germination and seedling growth among rice subspecies [ 16 ]; according to the sequence variation, its promoter can be characterized into two types, including a flooding-tolerant type (T-type) that only exists in japonica lowland cultivars and a flooding-intolerant type (I-type) that exists in japonica upland-, and indica upland/lowland-, cultivars. The flooding-intolerant cultivars that contain an I-type promoter can downregulate CIPK15 protein accumulation by inducing the expression of OsCBL10 .…”

“…The flooding-intolerant cultivars that contain an I-type promoter can downregulate CIPK15 protein accumulation by inducing the expression of OsCBL10 . In contrast, the cultivars containing a T-type promoter have downregulated OsCBL10 transcription, higher αAmy activity, and increased CIPK15 protein accumulation [ 16 ]. Furthermore, however, the OsCBL10 -overexpressing line is more sensitive to flooding stress than the wild type, suggesting that CBL10 negatively regulates the CIPK15-SnRK1A-MYBS1 -mediated pathway [ 16 ].…”

“…Despite the sophisticated molecular mechanisms involved in the regulation of the anaerobic germination and seedling growth in rice, considerable progress on understanding the genetic, molecular and physiological basis of rice in response to submergence stress at the germination stage, has been achieved in the last few decades [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Here, we mainly focus on reviewing the molecular genetic mechanisms that regulate the metabolic adaptation of rice to anaerobic germination stress; we could not cover all the related advances due to space limitations.…”

Molecular Mechanisms Supporting Rice Germination and Coleoptile Elongation under Low Oxygen

“…Although it is not clear how the mechanism functions under O 2 deprivation, CBL4 was found to interact with CIPK15 [ 34 ] to positively regulate downstream events. On the contrary, CBL10 has been found to be a negative regulator of the CIPK15-dependent pathway since the maintenance of a low CBL10 expression level in some rice varieties allows a higher expression of AMY3 [ 35 ]. In the activation cascade, CIPK15 was shown to regulate the major sugar regulatory kinase SUCROSE NONFERMETNING 1-RELATED PROTEIN KINASE SnRK1A that subsequently activates the MYELOBLASTOSIS SUCROSE 1 (MYBS1) transcription factor involved in the transcriptional regulation of α-amylase genes [ 36 , 37 , 38 ].…”

The Analysis of Pinus pinaster SnRKs Reveals Clues of the Evolution of This Family and a New Set of Abiotic Stress Resistance Biomarkers

“…SnRK kinases participate in the stress response both through the direct modulation of stress response effectors as ion channels, and the regulation of transcription factors-bZIP family-and epigenetic modulation mechanisms such as the SWI/SNF complex, which in turn control the expression of broad stress-related gene groups. The modulation of the expression of the SnRKs and/or their related elements as bZIP transcription factors through the use of genetic engineering or approaches exploiting their natural variation enhances stress resistance into both herbaceous species as A. thaliana and rice, and tree species as poplar [14,19,20]. Moreover, SnRKs are linked to the modulation of different agronomical traits under stress including wood quality.…”