Cyclic Nucleotide Gated Ion Channels (CNGCs) have been firmly established as Ca2+-conducting ion channels that regulate a wide variety of physiological responses in plants. CNGC2 has been implicated in plant immunity and Ca2+ signaling due to the autoimmune phenotypes exhibited by null mutants of CNGC2 in Arabidopsis thaliana. However, cngc2 mutants display additional phenotypes that are unique among autoimmune mutants, suggesting that CNGC2 has functions beyond defense and generates distinct Ca2+ signals in response to different triggers. In this study we found that cngc2 mutants showed reduced gravitropism, consistent with a defect in auxin signaling. This was mirrored in the diminished auxin response detected by the auxin reporters DR5::GUS and DII-VENUS and in a strongly impaired auxin-induced Ca2+ response. Moreover, the cngc2 mutant exhibits higher levels of the endogenous auxin indole-3-acetic acid (IAA), indicating that excess auxin in the cngc2 mutant causes its pleiotropic phenotypes. These auxin signaling defects and the autoimmunity syndrome of the cngc2 mutant could be suppressed by loss-of-function mutations in the auxin biosynthesis gene YUCCA6 (YUC6), as determined by identification of the cngc2 suppressor mutant repressor of cngc2 (rdd1) as an allele of YUC6. A loss-of-function mutation in the upstream auxin biosynthesis gene TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA1, WEAK ETHYLENE INSENSITIVE8) also suppressed the cngc2 phenotypes, further supporting the tight relationship between CNGC2 and the TAA–YUC-dependent auxin biosynthesis pathway. Taking these results together, we propose that the Ca2+ signal generated by CNGC2 is a part of the negative feedback regulation of auxin homeostasis in which CNGC2 balances cellular auxin perception by influencing auxin biosynthesis.

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Euphorbia lagascae and Centrapalus pauciflorus are natural sources of the plasticizer vernolic acid, and are therefore being considered as potentially new industrial oilseed crops in Canada. Both species show a propensity to grow in undisturbed and unfavourable conditions in their native regions of southern Europe and Africa. Trials were conducted in Ontario between 2013 and 2014 to better understand the biology of these species. The ability of these species to establish, leave a seedbank, and compete with a crop was explored. C. pauciflorus emergence in cultivated seedbeds (5.14%-12.15%) was higher than in mowed (0.99%-1.87%) and undisturbed grass (0.00%-0.25%) in spring 2014. E. lagascae also emerged at higher rates in cultivated seedbeds (3.07%-4.98%) than mowed (0.88%-1.99%) or undisturbed grass (0.22%-1.00%) in spring 2014, however emergence was higher in mowed grass (6.25%) than seedbeds (4.00%) in fall 2014. The low persistence of seeds in the soil (93%-100% seeds were nonviable) and poor ability to establish a seedbank limit their potential as weeds. Plants that established in unmanaged areas did not produce viable seeds and are therefore unlikely to become weeds. Even though their competitive ability is similar to that of redroot pigweed on a plant per plant basis, they are unlikely to achieve the high densities and persistence of pigweed infestation and are unlikely to threaten farms as weeds.

Surveillance data on grain yield and diseases, insect pests and weeds from farmers' fields for two consecutive wet seasons (1981 and 1982) grouped into dwarf indica (dwarf) and tall indica (tall) rice varieties were subjected to multiple regression analysis. Equations having r ~ or R ~ ~ 0.60 are reported. Bacterial leaf streak alone explained 70% of yield variation in dwarf varieties, leaf blast and bacterial leaf streak together explained a yield variation of 74%. Brown spot and tungro diseases showed little increase in percentage yield variation in tall varieties. Among the insect pests, yellow stem borer alone could explain 69% yield variation in dwarf and 62% in tall varieties. Narrow-leaf weeds contributed more towards yield variation than did broad-leaf weeds. A combination of pests explained variations in yield better than did any individual pest.

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