Abstract
Starch provides plants with carbon and energy during stressful periods; however, relatively few regulators of starch metabolism under stress-induced carbon starvation have been discovered. We studied a protein kinase Ser/Thr/Tyr (STY) 46, identified by gene co-expression network analysis as a potential regulator of the starch starvation response in Arabidopsis thaliana. We showed that STY46 was induced by (1) abscisic acid and prolonged darkness, (2) by abiotic stressors, including salinity and osmotic stress, and (3) by conditions associated with carbon starvation. Characterization of STY46 T-DNA knockout mutants indicated that there was functional redundancy among the STY gene family, as these genotypes did not show strong phenotypes. However, Arabidopsis with high levels of STY46 transcripts (OE-25) grew faster at the early seedling stage, had higher photosynthetic rates, and more carbon was stored as protein in the seeds under control conditions. Further, OE-25 source leaf accumulated more sugars under 100 mM NaCl stress, and salinity also accelerated root growth, which is consistent with an adaptive response. Salt-stressed OE-25 partitioned 14C towards sugars and amino acids, and away from starch and protein in source leaves. Together, these findings suggested that STY46 may be part of the salinity stress response pathway that utilizes starch during early plant growth.
Highlights
Many plants experience unfavorable environments during their lifecycle [1]
Ser/Thr/Tyr kinase isoform 46 (STY46) transcript was affected by hormones, light intensity and quality, nutrient status, photoperiodicity, and some abiotic stresses
Our work suggests the activation of a regulatory mechanism, whereby carbon is preferentially partitioned into osmoprotectants at the expense of storage compounds as a positive way to respond to salinity stress [34]
Summary
Many plants experience unfavorable environments during their lifecycle [1]. These environments often alter plants’ ability to assimilate, partition, allocate, and store carbohydrates [2,3,4]. Once sugar starvation is detected, signal transduction cascades are activated, which alter gene expression [11], leading to the metabolism of cytosolic and storage proteins [8,12,13,14,15,16]. If control conditions are restored in a timely fashion, plants may resume growth. These series of events, called the sugar starvation
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